Protected particles of cathode active materials for lithium batteries

ABSTRACT

Provided is a lithium battery cathode electrode comprising multiple particulates of a cathode active material, wherein at least a particulate comprises one or a plurality of particles of a cathode active material being encapsulated by a thin layer of a sulfonated elastomer, wherein the encapsulating thin layer of sulfonated elastomer has a thickness from 1 nm to 10 μm, a fully recoverable tensile strain from 2% to 800%, and a lithium ion conductivity from 10 −7  S/cm to 5×10 −2  S/cm. The encapsulating layer may further contain an electron-conducting additive and/or a lithium ion-conducting additive dispersed in the sulfonated elastomer.

FIELD OF THE INVENTION

The present invention relates generally to the field of rechargeablelithium battery and, more particularly, to the cathode active materialsin the form of particulates containing transition metal oxide-filledelastomer-encapsulated cathode active material particles and the methodof producing same.

BACKGROUND OF THE INVENTION

A unit cell or building block of a lithium-ion battery is typicallycomposed of an anode current collector, an anode or negative electrodelayer (containing an anode active material responsible for storinglithium therein, a conductive additive, and a resin binder), anelectrolyte and porous separator, a cathode or positive electrode layer(containing a cathode active material responsible for storing lithiumtherein, a conductive additive, and a resin binder), and a separatecathode current collector. The electrolyte is in ionic contact with boththe anode active material and the cathode active material. A porousseparator is not required if the electrolyte is a solid-stateelectrolyte.

The binder in the anode layer is used to bond the anode active material(e.g. graphite or Si particles) and a conductive filler (e.g. carbonblack particles or carbon nanotube) together to form an anode layer ofstructural integrity, and to bond the anode layer to a separate anodecurrent collector, which acts to collect electrons from the anode activematerial when the battery is discharged. In other words, in the negativeelectrode (anode) side of the battery, there are typically fourdifferent materials involved: an anode active material, a conductiveadditive, a resin binder (e.g. polyvinylidine fluoride, PVDF, orstyrene-butadiene rubber, SBR), and an anode current collector(typically a sheet of Cu foil). Typically the former three materialsform a separate, discrete anode active material layer (or, simply, anodelayer) and the latter one forms another discrete layer (currentcollector layer). A binder resin (e.g. PVDF or PTFE) is also used in thecathode to bond cathode active materials and conductive additiveparticles together to form a cathode active layer of structuralintegrity. The same resin binder also acts to bond this cathode activelayer to a cathode current collector (e.g. Al foil).

Historically, lithium-ion batteries actually evolved from rechargeable“lithium metal batteries” that use lithium (Li) metal as the anode and aLi intercalation compound (e.g. MoS₂) as the cathode. Li metal is anideal anode material due to its light weight (the lightest metal), highelectronegativity (−3.04 V vs. the standard hydrogen electrode), andhigh theoretical capacity (3,860 mAh/g). Based on these outstandingproperties, lithium metal batteries were proposed 40 years ago as anideal system for high energy-density applications.

Due to some safety concerns (e.g. lithium dendrite formation andinternal shorting) of pure lithium metal, graphite was implemented as ananode active material in place of the lithium metal to produce thecurrent lithium-ion batteries. The past two decades have witnessed acontinuous improvement in Li-ion batteries in terms of energy density,rate capability, and safety. However, the use of graphite-based anodesin Li-ion batteries has several significant drawbacks: low specificcapacity (theoretical capacity of 372 mAh/g as opposed to 3,860 mAh/gfor Li metal), long Li intercalation time (e.g. low solid-statediffusion coefficients of Li in and out of graphite and inorganic oxideparticles) requiring long recharge times (e.g. 7 hours for electricvehicle batteries), inability to deliver high pulse power (powerdensity<0.5 kW/kg), and necessity to use prelithiated cathodes (e.g.lithium cobalt oxide, as opposed to cobalt oxide), thereby limiting thechoice of available cathode materials.

Further, these commonly used cathode active materials have a relativelylow specific capacity (typically <220 mAh/g). These factors havecontributed to the two major shortcomings of today's Li-ion batteries—alow energy density (typically 150-220 Wh/kg_(cell)) and low powerdensity (typically <0.5 kW/kg). In addition, even though the lithiummetal anode has been replaced by an intercalation compound (e.g.graphite) and, hence, there is little or no lithium dendrite issue inthe lithium-ion battery, the battery safety issue has not gone away.There have been no short of incidents involving lithium-ion batteriescatching fire or exploding. To sum it up, battery scientists have beenfrustrated with the low energy density, inadequate cycle life, andflammability of lithium-ion cells for over three decades!

There have been tremendous efforts made in battery industry and researchcommunity to improve existing cathode materials and develop new cathodecompositions. However, current and emerging cathode active materials forlithium secondary batteries still suffer from the following seriousdrawbacks:

-   -   (1) The most commonly used cathode active materials (e.g.        lithium transition metal oxides) contain a transition metal        (e.g. Fe, Mn, Co, Ni, etc.) that is a powerful catalyst that can        promote undesirable chemical reactions inside a battery (e.g.        decomposition of electrolyte). These cathode active materials        also contain a high oxygen content that could assist in the        progression of thermal runaway and provide oxygen for        electrolyte oxidation, increasing the danger of explosion or        fire hazard. This is a serious problem that has hampered the        widespread implementation of electric vehicles.    -   (2) Most of promising organic or polymeric cathode active        materials are either soluble in the commonly used electrolytes        or are reactive with these electrolytes. Dissolution of active        material in the electrolyte results in a continuing loss of the        active material. Undesirable reactions between the active        material and the electrolyte lead to graduate depletion of the        electrolyte and the active material in the battery cell. All        these phenomena lead to capacity loss of the battery and        shortened cycle life.    -   (3) The practical capacity achievable with current cathode        materials (e.g. lithium iron phosphate and lithium transition        metal oxides) has been limited to the range of 150-250 mAh/g        and, in most cases, less than 200 mAh/g. Additionally, emerging        high-capacity cathode active materials (e.g. FeF₃) still cannot        deliver a long battery cycle life.        -   High-capacity cathode active materials, such as metal            fluoride, metal chloride, and lithium transition metal            silicide, can undergo large volume expansion and shrinkage            during the discharge and charge of a lithium battery. These            repeated volume changes lead to structural instability of            the cathode, breakage of the normally weak bond between the            binder resin and the active material, fragmentation of            active material particles, delamination between the cathode            active material layer and the current collector, and            interruption of electron-conducting pathways. These            high-capacity cathodes include CoF₃, MnF₃, FeF₃, VF₃, VOF₃,            TiF₃, BiF₃, NiF₂, FeF₂, CuF₂, CuF, SnF₂, AgF, CuCl₂, FeCl₃,            MnCl₂, etc. High-capacity cathode active materials also            include a lithium transition metal silicate, Li₂MSiO₄ or            Li₂Ma_(x)Mb_(y)SiO₄, wherein M and Ma are selected from Fe,            Mn, Co, Ni, V, or VO; Mb is selected from Fe, Mn, Co, Ni, V,            Ti, Al, B, Sn, or Bi; and x+y≤1.

Hence, there is an urgent and continuing need for a new cathode activematerial and a cathode electrode (e.g. a cathode active material layer)that enable a lithium secondary battery to deliver a long cycle life andhigher energy density. There is also a need for a method of readily andeasily producing such a material in large quantities. Thus, it is aprimary object of the present invention to meet these needs and addressthe issues associated the rapid capacity decay of a lithium battery.

SUMMARY OF THE INVENTION

Herein reported is a cathode active material layer or electrode (acathode electrode or positive electrode) for a lithium battery thatcontains a very unique class of cathode active materials. The cathodeactive material is in a form of particulates, wherein at least aparticulate contains one or a plurality of particles of a cathode activematerial being embraced or encapsulated by a thin layer of a sulfonatedelastomer. This new class of material is capable of overcoming thecathode-induced rapid capacity decay problem commonly associated with arechargeable lithium battery.

The cathode electrode comprises multiple particulates of a cathodeactive material, wherein at least a particulate is composed of one or aplurality of the cathode active material particles that are encapsulatedby a thin layer of sulfonated elastomer, wherein the encapsulating thinlayer of sulfonated elastomer has a thickness from 1 nm to 10 μm, afully recoverable tensile strain from 2% to 800%, and a lithium ionconductivity from 10⁻⁷ S/cm to 5×10⁻² S/cm.

The encapsulating thin layer of sulfonated elastomer has a fullyrecoverable tensile strain from 2% to 800% (more typically from 5% to300% and most typically from 10% to 150%), a thickness from 1 nm to 10μm, and a lithium ion conductivity from 10⁻⁷ S/cm to 5×10⁻² S/cm (moretypically from 10⁻⁵ S/cm to 10⁻³ S/cm) when measured at room temperatureon a cast thin film 20 μm thick. Preferably, this thin encapsulatinglayer also has an electrical conductivity from 10⁻⁷ S/cm to 100 S/cm(more typically from 10⁻³ S/cm to 10 S/cm when an electron-conductingadditive is added into the sulfonated elastomer matrix material).

Preferably, the elastomeric matrix material contains a sulfonatedversion of an elastomer selected from natural polyisoprene, syntheticpolyisoprene, polybutadiene, chloroprene rubber, polychloroprene, butylrubber, styrene-butadiene rubber, nitrile rubber, ethylene propylenerubber, ethylene propylene diene rubber, metallocene-basedpoly(ethylene-co-octene) (POE) elastomer, poly(ethylene-co-butene) (PBE)elastomer, styrene-ethylene-butadiene-styrene (SEBS) elastomer,epichlorohydrin rubber, polyacrylic rubber, silicone rubber,fluorosilicone rubber, perfluoroelastomers, polyether block amides,chlorosulfonated polyethylene, ethylene-vinyl acetate, thermoplasticelastomer, protein resilin, protein elastin, ethyleneoxide-epichlorohydrin copolymer, polyurethane, urethane-urea copolymer,or a combination thereof. These sulfonated elastomers or rubbers, whenpresent without an additive, exhibit a high elasticity (having a fullyrecoverable tensile strain from 2% to 800%). In other words, they can bestretched up to 800% (8 times of the original length when under tension)and, upon release of the tensile stress, they can fully recover back tothe original dimension. By adding from 0.01% to 50% by weight of anadditive (e.g. graphene sheets, CNTs, carbon black, lithium salt, etc.)dispersed in a sulfonated elastomeric matrix material, the fullyrecoverable tensile strains are typically reduced down to 2%-500% (moretypically from 5% to 300% and most typically from 10% to 150%).

In certain preferred embodiments, the sulfonated elastomer furthercontains an electron-conducting filler dispersed in the sulfonatedelastomer wherein the electron-conducting filler is selected from acarbon nanotube, carbon nanofiber, nanocarbon particle, metalnanoparticle, metal nanowire, electron-conducting polymer, graphene, ora combination thereof. The graphene may be preferably selected frompristine graphene, graphene oxide, reduced graphene oxide, graphenefluoride, graphene chloride, nitrogenated graphene, hydrogenatedgraphene, doped graphene, functionalized graphene, or a combinationthereof and the graphene preferably comprises single-layer graphene orfew-layer graphene, wherein the few-layer graphene is defined as agraphene platelet formed of less than 10 graphene planes. Theelectron-conducting polymer is preferably selected from (but not limitedto) polyaniline, polypyrrole, polythiophene, polyfuran, a bi-cyclicpolymer, a sulfonated derivative thereof, or a combination thereof.

Preferably, the graphene sheets have a lateral dimension (length orwidth) from 5 nm to 5 μm, more preferably from 10 nm to 1 μm, and mostpreferably from 10 nm to 300 nm. Shorter graphene sheets allow foreasier encapsulation and enable faster lithium ion transport through theinorganic filler-reinforced elastomer-based encapsulating layer.

Preferably, the particulates are substantially or essentially sphericalor ellipsoidal in shape. Also preferably, the particulate have adiameter or thickness smaller than 30 μm, more preferably smaller than20 μm, and most preferably smaller than 10 μm.

The cathode active material particulate may contain a cathode activematerial selected from an inorganic material, an organic material, apolymeric material, or a combination thereof. The inorganic material maybe selected from a metal oxide, metal phosphate, metal silicide, metalselenide, transition metal sulfide, sulfur, lithium polysulfide,selenium, lithium selenide, or a combination thereof.

The inorganic material may be selected from a lithium cobalt oxide,lithium nickel oxide, lithium manganese oxide, lithium vanadium oxide,lithium-mixed metal oxide, lithium iron phosphate, lithium manganesephosphate, lithium vanadium phosphate, lithium mixed metal phosphate,lithium metal silicide, or a combination thereof.

In certain preferred embodiments, the inorganic material-based cathodeactive material is selected from a metal fluoride or metal chlorideincluding the group consisting of CoF₃, MnF₃, FeF₃, VF₃, VOF₃, TiF₃,BiF₃, NiF₂, FeF₂, CuF₂, CuF, SnF₂, AgF, CuCl₂, FeCl₃, MnCl₂, andcombinations thereof. In certain preferred embodiments, the inorganicmaterial is selected from a lithium transition metal silicate, denotedas Li₂MSiO₄ or Li₂Ma_(x)Mb_(y)SiO₄, wherein M and Ma are selected fromFe, Mn, Co, Ni, V, or VO; Mb is selected from Fe, Mn, Co, Ni, V, Ti, Al,B, Sn, or Bi; and x+y≤1.

In certain preferred embodiments, the inorganic material is selectedfrom a transition metal dichalcogenide, a transition metaltrichalcogenide, or a combination thereof. The inorganic material isselected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, COO₂, an iron oxide, avanadium oxide, or a combination thereof.

The cathode active material layer may contain a metal oxide containingvanadium oxide selected from the group consisting of VO₂, Li_(x)VO₂,V₂O₅, Li_(x)V₂O₅, V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉, Li_(x)V₄O₉, V₆O₁₃,Li_(x)V₆O₁₃, their doped versions, their derivatives, and combinationsthereof, wherein 0.1<x<5.

The cathode active material layer may contain a metal oxide or metalphosphate, selected from a layered compound LiMO₂, spinel compoundLiM₂O₄, olivine compound LiMPO₄, silicate compound Li₂MSiO₄, tavoritecompound LiMPO₄F, borate compound LiMBO₃, or a combination thereof,wherein M is a transition metal or a mixture of multiple transitionmetals.

In some embodiments, the inorganic material is selected from: (a)bismuth selenide or bismuth telluride, (b) transition metaldichalcogenide or trichalcogenide, (c) sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, cobalt, manganese, iron, nickel, or a transition metal; (d)boron nitride, or (e) a combination thereof.

The cathode active material layer may contain an organic material orpolymeric material selected from poly(anthraquinonyl sulfide) (PAQS), alithium oxocarbon, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, quino(triazene), redox-active organic material,tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,hexaazatrinaphtylene (HATN), hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-benzylidene hydantoin, isatine lithium salt, pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected frompoly[methanetetryl-tetra(thiomethylene)](PMTTM),poly(2,4-dithiopentanylene) (PDTP), a polymer containingpoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, poly(2-phenyl-1,3-dithiolane) (PPDT),poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).

In other embodiments, the cathode active material layer contains anorganic material selected from a phthalocyanine compound, such as copperphthalocyanine, zinc phthalocyanine, tin phthalocyanine, ironphthalocyanine, lead phthalocyanine, nickel phthalocyanine, vanadylphthalocyanine, fluorochromium phthalocyanine, magnesium phthalocyanine,manganous phthalocyanine, dilithium phthalocyanine, aluminumphthalocyanine chloride, cadmium phthalocyanine, chlorogalliumphthalocyanine, cobalt phthalocyanine, silver phthalocyanine, ametal-free phthalocyanine, a chemical derivative thereof, or acombination thereof.

The cathode active material is preferably in a form of nanoparticle(spherical, ellipsoidal, and irregular shape), nanowire, nanofiber,nanotube, nanosheet, nanobelt, nanoribbon, nanodisc, nanoplatelet, ornanohorn having a thickness or diameter less than 100 nm. These shapescan be collectively referred to as “particles” unless otherwisespecified or unless a specific type among the above species is desired.Further preferably, the cathode active material has a dimension lessthan 50 nm, even more preferably less than 20 nm, and most preferablyless than 10 nm.

In some embodiments, one particle or a cluster of particles may becoated with or embraced by a layer of carbon disposed between the activematerial particle(s) and the protecting sulfonated elastomer layer (theencapsulating shell). Alternatively or additionally, a carbon layer maybe deposited to embrace the encapsulated particle or the encapsulatedcluster of multiple cathode active material particles.

The particulate may further contain a graphite or carbon material mixedwith the active material particles, which are all encapsulated by theencapsulating shell (but not dispersed within this thin layer ofsulfonated elastomer). The carbon or graphite material is selected frompolymeric carbon, amorphous carbon, chemical vapor deposition carbon,coal tar pitch, petroleum pitch, mesophase pitch, carbon black, coke,acetylene black, activated carbon, fine expanded graphite particle witha dimension smaller than 100 nm, artificial graphite particle, naturalgraphite particle, or a combination thereof.

The cathode active material particles may be coated with or embraced bya conductive protective coating (selected from a carbon material,electronically conductive polymer, conductive metal oxide, or conductivemetal coating) prior to being encapsulated by the sulfonated elastomershell.

Preferably and typically, the sulfonated elastomer has a lithium ionconductivity no less than 10⁻⁶ S/cm, more preferably no less than 5×10⁻⁵S/cm. In certain embodiments, the sulfonated elastomer further containsfrom 0.1% to 40% by weight (preferably from 1% to 30% by weight) of alithium ion-conducting additive dispersed in the sulfonated elastomermatrix material.

In some embodiments, the sulfonated elastomeric matrix material containsa material selected from a sulfonated version of natural polyisoprene(e.g. cis-1,4-polyisoprene natural rubber (NR) andtrans-1,4-polyisoprene gutta-percha), synthetic polyisoprene (IR forisoprene rubber), polybutadiene (BR for butadiene rubber), chloroprenerubber (CR), polychloroprene (e.g. Neoprene, Baypren etc.), butyl rubber(copolymer of isobutylene and isoprene, IIR), including halogenatedbutyl rubbers (chloro butyl rubber (CIIR) and bromo butyl rubber (BIIR),styrene-butadiene rubber (copolymer of styrene and butadiene, SBR),nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), EPM(ethylene propylene rubber, a copolymer of ethylene and propylene), EPDMrubber (ethylene propylene diene rubber, a terpolymer of ethylene,propylene and a diene-component), metallocene-basedpoly(ethylene-co-octene) (POE) elastomer, poly(ethylene-co-butene) (PBE)elastomer, styrene-ethylene-butadiene-styrene (SEBS) elastomer,epichlorohydrin rubber (ECO), polyacrylic rubber (ACM, ABR), siliconerubber (SI, Q, VMQ), fluorosilicone rubber (FVMQ), fluoroelastomers(FKM, and FEPM; such as Viton, Tecnoflon, Fluorel, Aflas and Dai-El),perfluoroelastomers (FFKM: Tecnoflon PFR, Kalrez, Chemraz, Perlast),polyether block amides (PEBA), chlorosulfonated polyethylene (CSM; e.g.Hypalon), and ethylene-vinyl acetate (EVA), thermoplastic elastomers(TPE), protein resilin, protein elastin, ethylene oxide-epichlorohydrincopolymer, polyurethane, urethane-urea copolymer, and combinationsthereof. Sulfonation imparts higher lithium ion conductivity to theelastomer.

In some preferred embodiments, the sulfonated elastomer further containsa lithium ion-conducting additive dispersed in an elastomer matrixmaterial, wherein the lithium ion-conducting additive is selected fromLi₂CO₃, Li₂O, Li₂C₂O₄, LiOH, LiX, ROCO₂Li, HCOLi, ROLi, (ROCO₂Li)₂,(CH₂OCO₂Li)₂, Li₂S, Li_(x)SO_(y), or a combination thereof, wherein X=F,Cl, I, or Br, R=a hydrocarbon group, 0<x≤1 and 1≤y≤4.

In some embodiments, the sulfonated elastomer further contains a lithiumion-conducting additive dispersed therein, wherein the lithiumion-conducting additive contains a lithium salt selected from lithiumperchlorate (LiClO₄), lithium hexafluorophosphate (LiPF₆), lithiumborofluoride (LiBF₄), lithium hexafluoroarsenide (LiAsF₆), lithiumtrifluoro-methanesulfonate (LiCF₃SO₃), bis-trifluoromethyl sulfonylimidelithium (LiN(CF₃SO₂)₂), lithium bis(oxalato)borate (LiBOB), lithiumoxalyldifluoroborate (LiBF₂C₂O₄), lithium nitrate (LiNO₃),Li-fluoroalkyl-phosphate (LiPF₃(CF₂CF₃)₃), lithiumbisperfluoro-ethylsulfonylimide (LiBETI), lithiumbis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide,lithium trifluoromethanesulfonimide (LiTFSI), an ionic liquid-basedlithium salt, or a combination thereof.

The proportion of this lithium ion-conducing additive is preferably from0.1% to 40% by weight, but more preferably from 1% to 25% by weight. Thesum of this additive and other additives preferably occupies from 1% to40% by weight, more preferably from 3% to 35% by weight, and mostpreferably from 5% to 25% by weight of the resulting composite weight(the elastomer matrix, electron-conducting additive, and lithiumion-conducting additive combined).

In certain preferred embodiments, the elastomeric matrix material maycontain a mixture or blend of a sulfonated elastomer and anelectron-conducting polymer selected from polyaniline, polypyrrole,polythiophene, polyfuran, a bi-cyclic polymer, derivatives thereof (e.g.sulfonated versions of these electron-conducting polymers), or acombination thereof. The proportion of this electron-conducting polymeris preferably from 0.1% to 20% by weight.

In some embodiments, the elastomeric matrix material contains a mixtureor blend of a sulfonated elastomer and a lithium ion-conducting polymerselected from poly(ethylene oxide) (PEO), polypropylene oxide (PPO),poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA),poly(vinylidene fluoride) (PVDF), poly bis-methoxyethoxyethoxide-phosphazene, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, or a combination thereof. Sulfonation is hereinfound to impart improved lithium ion conductivity to a polymer. Theproportion of this lithium ion-conducting polymer is preferably from0.1% to 20% by weight. Mixing or dispersion of an additive orreinforcement species in a sulfonated elastomer or rubber may beconducted using solution mixing or melt mixing.

The present invention also provides a powder mass of cathode activematerial for a lithium battery. The powder mass comprises multipleparticulates of a cathode active material, wherein at least oneparticulate is composed of one or a plurality of the cathode activematerial particles that are encapsulated by a thin layer of sulfonatedelastomer. The encapsulating thin layer of sulfonated elastomer has athickness from 1 nm to 10 μm, a fully recoverable tensile strain from 2%to 500%, and a lithium ion conductivity from 10⁻⁷ S/cm to 5×10⁻² S/cm.

The present invention also provides a cathode electrode that containsthe presently invented sulfonated elastomer-encapsulated cathodematerial particles, an optional conductive additive (e.g. expandedgraphite flakes, carbon black, acetylene black, or carbon nanotube), andan optional resin binder (typically required).

The present invention also provides a lithium battery containing anoptional cathode current collector (e.g. Al foil), the presentlyinvented cathode electrode as described above, an anode active materiallayer or anode electrode, an optional anode current collector (e.g. Cufoil), an electrolyte in ionic contact with the anode active materiallayer and the cathode active material layer and an optional porousseparator.

There is no limitation on the type of anode active material that can beused in the anode electrode to partner with the invented cathode. Forinstance, the anode active material may be selected from the groupconsisting of: (a) silicon (Si), germanium (Ge), tin (Sn), lead (Pb),antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti),nickel (Ni), cobalt (Co), and cadmium (Cd); (b) alloys or intermetalliccompounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Ni, Co, or Cd withother elements; (c) oxides, carbides, nitrides, sulfides, phosphides,selenides, and tellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Fe, Ni,Co, V, or Cd, and their mixtures, composites, or lithium-containingcomposites; (d) salts and hydroxides of Sn; (e) lithium titanate,lithium manganate, lithium aluminate, lithium-containing titanium oxide,lithium transition metal oxide; (f) prelithiated versions thereof, (g)particles and foil of Li, Li alloy, or surface-stabilized Li particleshaving at least 60% by weight of lithium element therein; and (h)combinations thereof.

In some preferred embodiments, the anode active material contains aprelithiated Si, prelithiated Ge, prelithiated Sn, prelithiated SnO_(x),prelithiated SiO_(x), prelithiated iron oxide, prelithiated VO₂,prelithiated Co₃O₄, prelithiated Ni₃O₄, or a combination thereof,wherein x=1 to 2. It may be noted that prelithiation of an anode activematerial means that this material has been pre-intercalated by or dopedwith lithium ions up to a weight fraction from 0.1% to 54.7% of Li inthe lithiated product.

The lithium battery may be a lithium-ion battery, lithium metal battery(containing lithium metal or lithium alloy as the main anode activematerial and containing no intercalation-based anode active material),lithium-sulfur battery, or lithium-selenium battery.

The invention also provides a method of producing a powder mass of acathode active material for a lithium battery, the method comprising:(a) mixing particles of an electron-conducting filler and/or a lithiumion-conducting filler and a sulfonated elastomer or its precursor (e.g.monomer or oligomer) in a liquid medium or solvent to form a suspension;(b) dispersing a plurality of particles of a cathode active material inthe suspension to form a slurry; and (c) dispensing the slurry andremoving the solvent and/or polymerizing/curing the precursor to formthe powder mass, wherein the powder mass comprises multiple particulatesof the cathode active material, wherein at least one of the particulatescomprises one or a plurality of the cathode active material particleswhich are encapsulated by a thin layer of sulfonated elastomer. Theencapsulating sulfonated elastomer has a thickness from 1 nm to 10 μm(preferably from 1 nm to 100 nm), a fully recoverable tensile strainfrom 2% to 800%, and a lithium ion conductivity from 10⁻⁷ S/cm to 10⁻²S/cm. Preferably, this encapsulating layer material also has anelectrical conductivity from 10⁻⁷ S/cm to 100 S/cm when measured at roomtemperature.

One can disperse an electron-conducting filler and/or a lithiumion-conducting filler in a monomer or oligomer (with or without asolvent; monomer itself being capable of serving as a liquid medium) toform a suspension. A chemical reaction may be optionally initiatedbetween filler particles, if any, and the monomer/oligomer at this stageor later. Cathode active material particles are then dispersed in thesuspension to form a slurry. A micro-encapsulation procedure (e.g.spray-drying) is then conducted to produce droplets (particulates),wherein a particulate can contain one or several cathode active materialparticles embraced/encapsulated by an elastomeric shell. The resultingparticulate is then subjected to a polymerization/curing treatment (e.g.via heating and/or UV curing, etc.). If the starting monomer/oligomeralready had sulfonate groups or were already sulfonated, the resultingreinforced elastomer shell would be a sulfonated elastomer composite.Otherwise, the resulting mass of particulates may be subsequentlysubjected to a sulfonating treatment.

Alternatively, one may dissolve a linear or branched chain polymer (butuncured or un-crosslinked) in a solvent to form a polymer solution. Sucha polymer can be a sulfonated polymer to begin with, or can besulfonated during any subsequent stage (e.g. after the particulates areformed). An electron-conducting additive and/or a lithium ion-conductingadditive, if desired, are then added into the polymer solution to form asuspension; particles of the cathode active material can be addedconcurrently or sequentially. The suspension is then subjected to amicro-encapsulation treatment to form particulates. Curing orcross-linking of the elastomer/graphene composite is then allowed toproceed.

Thus, the step of providing the solution and suspension may include (a)sulfonating an elastomer to form a sulfonated elastomer and dissolvingthe sulfonated elastomer in a solvent to form a polymer solution, or (b)sulfonating the precursor (monomer or oligomer) to obtain a sulfonatedprecursor (sulfonated monomer or sulfonated oligomer), polymerizing thesulfonated precursor to form a sulfonated elastomer and dissolving thesulfonated elastomer in a solvent to form a solution. Inorganic fillerparticles (optionally along with an electron-conducting additive and/ora lithium ion-conducting additive) and cathode active material particlesare concurrently or sequentially added into the solution to form asuspension.

In certain embodiments, the step of dispensing the slurry and removingthe solvent and/or polymerizing/curing the precursor to form the powdermass includes operating a procedure (e.g. micro-encapsulation) selectedfrom pan-coating, air-suspension coating, centrifugal extrusion,vibration-nozzle encapsulation, spray-drying, coacervation-phaseseparation, interfacial polycondensation and interfacial cross-linking,in-situ polymerization, matrix polymerization, or a combination thereof.

In this method, the step of mixing may include dissolving or dispersingfrom 0.1% to 40% by weight of a lithium ion-conducting additive in theliquid medium or solvent. The lithium ion-conducting additive may beselected from Li₂CO₃, Li₂O, Li₂C₂O₄, LiOH, LiX, ROCO₂Li, HCOLi, ROLi,(ROCO₂Li)₂, (CH₂OCO₂Li)₂, Li₂S, Li_(x)SO_(Y), or a combination thereof,wherein X=F, Cl, I, or Br, R=a hydrocarbon group, 0<x≤1 and 1≤y≤4.Alternatively or additionally, the lithium ion-conducting additivecontains a lithium salt selected from lithium perchlorate (LiClO₄),lithium hexafluorophosphate (LiPF₆), lithium borofluoride (LiBF₄),lithium hexafluoroarsenide (LiAsF₆), lithium trifluoro-methanesulfonate(LiCF₃SO₃), bis-trifluoromethyl sulfonylimide lithium (LiN(CF₃SO₂)₂),lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate(LiBF₂C₂O₄), lithium nitrate (LiNO₃), Li-fluoroalkyl-phosphate(LiPF₃(CF₂CF₃)₃), lithium bisperfluoro-ethylsulfonylimide (LiBETI),lithium bis(trifluoromethanesulfonyl)imide, lithiumbis(fluorosulfonyl)imide, lithium trifluoromethanesulfonimide (LiTFSI),an ionic liquid-based lithium salt, or a combination thereof.

In certain embodiments, the slurry further contains anelectron-conducting polymer selected from polyaniline, polypyrrole,polythiophene, polyfuran, a bi-cyclic polymer, a sulfonated derivativethereof, or a combination thereof. Alternatively or additionally, theslurry further contains a lithium ion-conducting polymer selected frompoly(ethylene oxide) (PEO), polypropylene oxide (PPO),poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA),poly(vinylidene fluoride) (PVDF), poly bis-methoxyethoxyethoxide-phosphazene, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, or a combination thereof.

The method may further comprise mixing multiple particulates of theaforementioned cathode active material, a binder resin, and an optionalconductive additive to form a cathode electrode, which is optionallycoated on a cathode current collector (e.g. Al foil). The method mayfurther comprise combining an anode electrode, the presently inventedcathode electrode (positive electrode), an electrolyte, and an optionalporous separator into a lithium battery cell.

The presently invented sulfonated elastomer-encapsulated active materialparticles meet all of the criteria required of a lithium-ion batterycathode material:

-   -   (a) The protective sulfonated elastomer shell, having both high        elasticity and high strength, has a high fracture toughness and        high resistance to crack formation to avoid disintegration        during repeated cycling.    -   (b) The sulfonated elastomer shell is relatively inert        (inactive) with respect to the electrolyte. Further, since there        is no direct contact between the cathode active material        particles and liquid electrolyte, there is no opportunity for        the transition metal in the cathode active material to catalyze        the decomposition of electrolyte, which otherwise could generate        undesirable chemical species (e.g. volatile molecules) inside        the battery cell.    -   (c) The sulfonated elastomer shell material can be both lithium        ion-conducting and electron-conducting.    -   (d) The encapsulating shell is capable of preventing any organic        cathode active material or certain inorganic cathode active        material (e.g. S, Se, lithium polysulfide, or lithium        polyselenide) from getting dissolved in a liquid electrolyte        and, as such, is capable of helping to prevent the shuttle        effect or other capacity-decaying mechanisms from occurring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) Schematic of a prior art lithium battery cell, wherein theanode layer is a thin Li foil and the cathode is composed of particlesof a cathode active material, a conductive additive (not shown) and aresin binder (not shown).

FIG. 1(B) Schematic of a prior art lithium-ion battery; the anode layerbeing composed of particles of an anode active material, a conductiveadditive (not shown) and a resin binder (not shown).

FIG. 2(A) Schematic illustrating the notion that expansion/shrinkage ofelectrode active material particles, upon lithium insertion andde-insertion during discharge/charge of a prior art lithium-ion battery,can lead to detachment of resin binder from the particles, interruptionof the conductive paths formed by the conductive additive, and loss ofcontact with the current collector;

FIG. 2(B) Several different types of particulates containing filledelastomer-encapsulated cathode active material particles.

FIG. 3 The specific intercalation capacity curves of four lithium cells:cathode containing un-encapsulated V₂O₅ particles, cathode containingun-encapsulated but graphene-embraced V₂O₅ particles, cathode containingsulfonated elastomer-encapsulated V₂O₅ particles, and cathode containingsulfonated elastomer-encapsulated graphene-embraced V₂O₅ particles.

FIG. 4 The specific capacity values of two lithium battery cells havinga cathode active material featuring (1) sulfonatedelastomer-encapsulated carbon-coated LiFePO₄ particles and (2)carbon-coated LiFePO₄ particles without sulfonated elastomerencapsulation, respectively.

FIG. 5 The discharge capacity curves of two coin cells having twodifferent types of cathode active materials: (1) sulfonatedelastomer-encapsulated metal fluoride particles and (2) non-encapsulatedmetal fluorides.

FIG. 6 Specific capacities of two lithium-FePc (organic) cells, eachhaving Li foil as an anode active material and FePc/RGO mixtureparticles as the cathode active material (one cell containingun-encapsulated particles and the other containing particlesencapsulated by a sulfonated elastomer).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is directed at a cathode active material layer (positiveelectrode layer, not including the cathode current collector) for alithium secondary battery. This positive electrode comprises a cathodeactive material that is in a form of a sulfonated elastomershell-protected particulate. The battery is preferably a secondarybattery based on a non-aqueous electrolyte, a polymer gel electrolyte,an ionic liquid electrolyte, a quasi-solid electrolyte, or a solid-stateelectrolyte. The shape of a lithium secondary battery can becylindrical, square, button-like, etc. The present invention is notlimited to any battery shape or configuration or any type ofelectrolyte.

As illustrated in FIG. 1(B), a lithium-ion battery cell is typicallycomposed of an anode current collector (e.g. Cu foil), an anode ornegative electrode active material layer (i.e. anode layer typicallycontaining particles of an anode active material, conductive additive,and binder), a porous separator and/or an electrolyte component, acathode or positive electrode active material layer (containing acathode active material, conductive additive, and resin binder), and acathode current collector (e.g. Al foil). More specifically, the cathodelayer comprises particles of a cathode active material, a conductiveadditive (e.g. carbon black particles), and a resin binder (e.g. SBR orPVDF). This cathode layer is typically 50-300 μm thick (more typically100-200 μm) to give rise to a sufficient amount of current per unitelectrode area.

In another cell configuration, as illustrated in FIG. 1(A), the anodeactive material is a lithium metal foil or a layer of packed Liparticles supported on an anode current collector, such as a sheet ofcopper foil. This can be a lithium metal secondary battery,lithium-sulfur battery, or lithium-selenium battery, etc.

In order to obtain a higher energy density lithium-ion cell, the anodein FIG. 1(B) can be designed to contain higher-capacity anode activematerials having a composition formula of Li_(a)A (A is a metal orsemiconductor element, such as Al and Si, and “a” satisfies 0<a≤5).These materials are of great interest due to their high theoreticalcapacity, e.g., Li₄Si (3,829 mAh/g), Li_(4.4)Si (4,200 mAh/g),Li_(4.4)Ge (1,623 mAh/g), Li_(4.4)Sn (993 mAh/g), Li₃Cd (715 mAh/g),Li₃Sb (660 mAh/g), Li_(4.4)Pb (569 mAh/g), LiZn (410 mAh/g), and Li₃Bi(385 mAh/g).

As schematically illustrated in FIG. 2(A), one major problem in thecurrent lithium battery is the notion that active material particles canget fragmented and the binder resin can detach from both the activematerial particles and conductive additive particles due to repeatedvolume expansion/shrinkage of the active material particles during thecharge and discharge cycles. These binder detachment and particlefragmentation phenomena lead to loss of contacts between active materialparticles and conductive additives and loss of contacts between theactive material and its current collector. These adverse effects resultin a significantly shortened charge-discharge cycle life.

We have solved these challenging issues that have troubled batterydesigners and electrochemists alike for more than 30 years by developinga new class of cathode active materials. The cathode active materiallayer comprises multiple cathode active material particles that arefully embraced or encapsulated by a sulfonated elastomer having arecoverable (elastic) tensile strain no less than 2% (up to 800%) underuniaxial tension and a lithium ion conductivity no less than 10⁻⁵ S/cmat room temperature (preferably and more typically from 1×10⁻⁵ S/cm to5×10⁻² S/cm).

As illustrated in FIG. 2(B), the present invention provides four majortypes of particulates of sulfonated elastomer-encapsulated cathodeactive material particles. The first one is a single-particleparticulate containing a cathode active material core 10 encapsulated bya high-elasticity sulfonated elastomer shell 12. The second is amultiple-particle particulate containing multiple cathode activematerial particles 14 (e.g. FeF₃ particles), optionally along with otherconductive materials (e.g. particles of graphite or hard carbon, notshown), which are encapsulated by a sulfonated elastomer 16. The thirdis a single-particle particulate containing a cathode active materialcore 18 coated by a carbon or graphene layer 20 (or other conductivematerial) further encapsulated by a sulfonated elastomer 22. The fourthis a multiple-particle particulate containing multiple cathode activematerial particles 24 (e.g. FeF₃ particles) coated with a conductiveprotection layer 26 (carbon, graphene, etc.), optionally along withother active materials or conductive additive, which are encapsulated bya sulfonated elastomer shell 28.

The elastomer refers to a polymer, typically a lightly cross-linkedpolymer, which exhibits an elastic deformation that is more typically atleast 5% when measured (without an additive or reinforcement in thepolymer) under uniaxial tension. In the field of materials science andengineering, the “elastic deformation” is defined as a deformation of amaterial (when being mechanically stressed) that is essentially fullyrecoverable and the recovery is essentially instantaneous upon releaseof the load. The elastic deformation is preferably greater than 5%, morepreferably greater than 10%, further more preferably greater than 50%,still more preferably greater than 100%, and most preferably greaterthan 200%. The preferred types of elastomer composites will be discussedlater.

The application of the presently invented elastomer compositeencapsulation approach is not limited to any particular class of cathodeactive materials. The cathode active material layer may contain acathode active material selected from an inorganic material, an organicmaterial, a polymeric material, or a combination thereof. The inorganicmaterial may be selected from a metal oxide, metal phosphate, metalsilicide, metal selenide, transition metal sulfide, or a combinationthereof.

The inorganic material, as a cathode active material, may be selectedfrom a lithium cobalt oxide, lithium nickel oxide, lithium manganeseoxide, lithium vanadium oxide, lithium-mixed metal oxide, lithium ironphosphate, lithium manganese phosphate, lithium vanadium phosphate,lithium mixed metal phosphate, lithium metal silicide, or a combinationthereof.

In certain embodiments, the inorganic filler for reinforcing theelastomer may be selected from an oxide, carbide, boride, nitride,sulfide, phosphide, or selenide of a transition metal, a lithiatedversion thereof, or a combination thereof. Preferably, the transitionmetal is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo,Pd, Ag, Cd, La, Ta, W, Pt, Au, Hg, a combination thereof, or acombination thereof with Al, Ga, In, Sn, Pb, Sb, or Bi.

In certain preferred embodiments, the sulfonated elastomer furthercontains an electron-conducting filler dispersed in the sulfonatedelastomer wherein the electron-conducting filler is selected from acarbon nanotube, carbon nanofiber, nanocarbon particle, metalnanoparticle, metal nanowire, electron-conducting polymer, graphene, ora combination thereof. The graphene may be preferably selected frompristine graphene, graphene oxide, reduced graphene oxide, graphenefluoride, graphene chloride, nitrogenated graphene, hydrogenatedgraphene, doped graphene, functionalized graphene, or a combinationthereof and the graphene preferably comprises single-layer graphene orfew-layer graphene, wherein the few-layer graphene is defined as agraphene platelet formed of 2-10 graphene planes. More preferably, thegraphene sheets contain 1-5 graphene planes, most preferably 1-3graphene planes (i.e. single-layer, double-layer, or triple-layergraphene). The electron-conducting polymer is preferably selected from(but not limited to) polyaniline, polypyrrole, polythiophene, polyfuran,a bi-cyclic polymer, a sulfonated derivative thereof, or a combinationthereof.

Preferably and typically, the sulfonated elastomer, when measuredwithout any additive, has a lithium ion conductivity from 10⁻⁷ S/cm to5×10⁻² S/cm, more preferably and typically greater than 10⁻⁵ S/cm,further more preferably and typically greater than 10⁻⁴ S/cm, and mostpreferably no less than 10⁻³ S/cm. In some embodiments, the sulfonatedelastomer further contains from 0.1% to 40% (preferably 1% to 35%) byweight of a lithium ion-conducting additive dispersed therein.

The sulfonated elastomer must have a high elasticity (high elasticdeformation value). By definition, an elastic deformation is adeformation that is fully recoverable upon release of the mechanicalstress and the recovery process is essentially instantaneous (nosignificant time delay). An elastomer, such as a vulcanized naturalrubber, can exhibit a tensile elastic deformation from 2% up to 1,000%(10 times of its original length). Sulfonation of the rubber reduces theelasticity to 800%. With the addition of 0.01%-50% of a conductivefiller (e.g. CNT and graphene sheets), the tensile elastic deformationof a sulfonated elastomer/rubber is reduced to typically from 2% to500%. It may be noted that although a metal typically has a highductility (i.e. can be extended to a large extent without breakage), themajority of the deformation is plastic deformation (non-recoverable) andelastic deformation occurs to only a small extent (typically <1% andmore typically <0.2%).

A broad array of sulfonated elastomers can be used to encapsulate acathode active material particle or multiple particles. Encapsulationmeans substantially fully embracing the particle(s) without allowing theparticle to be in direct contact with electrolyte in the battery. Thesulfonated elastomer may be selected from a sulfonated version ofnatural polyisoprene (e.g. cis-1,4-polyisoprene natural rubber (NR) andtrans-1,4-polyisoprene gutta-percha), synthetic polyisoprene (IR forisoprene rubber), polybutadiene (BR for butadiene rubber), chloroprenerubber (CR), polychloroprene (e.g. Neoprene, Baypren etc.), butyl rubber(copolymer of isobutylene and isoprene, IIR), including halogenatedbutyl rubbers (chloro butyl rubber (CIIR) and bromo butyl rubber (BIIR),styrene-butadiene rubber (copolymer of styrene and butadiene, SBR),nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), EPM(ethylene propylene rubber, a copolymer of ethylene and propylene), EPDMrubber (ethylene propylene diene rubber, a terpolymer of ethylene,propylene and a diene-component), metallocene-basedpoly(ethylene-co-octene) (POE) elastomer, poly(ethylene-co-butene) (PBE)elastomer, styrene-ethylene-butadiene-styrene (SEBS) elastomer,epichlorohydrin rubber (ECO), polyacrylic rubber (ACM, ABR), siliconerubber (SI, Q, VMQ), fluorosilicone rubber (FVMQ), fluoroelastomers(FKM, and FEPM; such as Viton, Tecnoflon, Fluorel, Aflas and Dai-El),perfluoroelastomers (FFKM: Tecnoflon PFR, Kalrez, Chemraz, Perlast),polyether block amides (PEBA), chlorosulfonated polyethylene (CSM; e.g.Hypalon), and ethylene-vinyl acetate (EVA), thermoplastic elastomers(TPE), protein resilin, protein elastin, ethylene oxide-epichlorohydrincopolymer, polyurethane, urethane-urea copolymer, and combinationsthereof.

The urethane-urea copolymer film usually consists of two types ofdomains, soft domains and hard domains. Entangled linear backbone chainsconsisting of poly(tetramethylene ether) glycol (PTMEG) units constitutethe soft domains, while repeated methylene diphenyl diisocyanate (MDI)and ethylene diamine (EDA) units constitute the hard domains. A lithiumion-conducting additive can be incorporated in the soft domains or othermore amorphous zones.

The electron-conducting filler may be selected from a carbon nanotube(CNT), carbon nanofiber, graphene, nanocarbon particles, metalnanowires, etc. A graphene sheet or nanographene platelet (NGP) composedof one basal plane (graphene plane) or multiple basal planes stackedtogether in the thickness direction. In a graphene plane, carbon atomsoccupy a 2-D hexagonal lattice in which carbon atoms are bonded togetherthrough strong in-plane covalent bonds. In the c-axis or thicknessdirection, these graphene planes may be weakly bonded together throughvan der Waals forces. An NGP can have a platelet thickness from lessthan 0.34 nm (single layer) to 100 nm (multi-layer). For the presentelectrode use, the preferred thickness is <10 nm, more preferably <3 nm(or <10 layers), and most preferably single-layer graphene. Thus, thepresently invented sulfonated elastomer/graphene composite shellpreferably contains mostly single-layer graphene, but could make use ofsome few-layer graphene (less than 10 layers or 10 graphene planes). Thegraphene sheet may contain a small amount (typically <25% by weight) ofnon-carbon elements, such as hydrogen, nitrogen, fluorine, and oxygen,which are attached to an edge or surface of the graphene plane.

Graphene sheets may be oxidized to various extents during theirpreparation, resulting in graphite oxide (GO) or graphene oxide. Hence,in the present context, graphene preferably or primarily refers to thosegraphene sheets containing no or low oxygen content; but, they caninclude GO of various oxygen contents. Further, graphene may befluorinated to a controlled extent to obtain graphite fluoride, or canbe doped using various dopants, such as boron and nitrogen.

Graphite oxide may be prepared by dispersing or immersing a laminargraphite material (e.g., powder of natural flake graphite or syntheticgraphite) in an oxidizing agent, typically a mixture of an intercalant(e.g., concentrated sulfuric acid) and an oxidant (e.g., nitric acid,hydrogen peroxide, sodium perchlorate, potassium permanganate) at adesired temperature (typically 0-70° C.) for a sufficient length of time(typically 30 minutes to 5 days). In order to reduce the time requiredto produce a precursor solution or suspension, one may choose to oxidizethe graphite to some extent for a shorter period of time (e.g., 30minutes) to obtain graphite intercalation compound (GIC). The GICparticles are then exposed to a thermal shock, preferably in atemperature range of 600-1,100° C. for typically 15 to 60 seconds toobtain exfoliated graphite or graphite worms, which are optionally (butpreferably) subjected to mechanical shearing (e.g. using a mechanicalshearing machine or an ultrasonicator) to break up the graphite flakesthat constitute a graphite worm. The un-broken graphite worms orindividual graphite flakes are then re-dispersed in water, acid, ororganic solvent and ultrasonicated to obtain a graphene polymer solutionor suspension.

The pristine graphene material is preferably produced by one of thefollowing three processes: (A) Intercalating the graphitic material witha non-oxidizing agent, followed by a thermal or chemical exfoliationtreatment in a non-oxidizing environment; (B) Subjecting the graphiticmaterial to a supercritical fluid environment for inter-graphene layerpenetration and exfoliation; or (C) Dispersing the graphitic material ina powder form to an aqueous solution containing a surfactant ordispersing agent to obtain a suspension and subjecting the suspension todirect ultrasonication.

In Procedure (A), a particularly preferred step comprises (i)intercalating the graphitic material with a non-oxidizing agent,selected from an alkali metal (e.g., potassium, sodium, lithium, orcesium), alkaline earth metal, or an alloy, mixture, or eutectic of analkali or alkaline metal; and (ii) a chemical exfoliation treatment(e.g., by immersing potassium-intercalated graphite in ethanolsolution).

In Procedure (B), a preferred step comprises immersing the graphiticmaterial to a supercritical fluid, such as carbon dioxide (e.g., attemperature T>31° C. and pressure P>7.4 MPa) and water (e.g., at T>374°C. and P>22.1 MPa), for a period of time sufficient for inter-graphenelayer penetration (tentative intercalation). This step is then followedby a sudden de-pressurization to exfoliate individual graphene layers.Other suitable supercritical fluids include methane, ethane, ethylene,hydrogen peroxide, ozone, water oxidation (water containing a highconcentration of dissolved oxygen), or a mixture thereof.

In Procedure (C), a preferred step comprises (a) dispersing particles ofa graphitic material in a liquid medium containing therein a surfactantor dispersing agent to obtain a suspension or slurry; and (b) exposingthe suspension or slurry to ultrasonic waves (a process commonlyreferred to as ultrasonication) at an energy level for a sufficientlength of time to produce the separated nanoscaled platelets, which arepristine, non-oxidized NGPs.

Reduced graphene oxide can be produced with an oxygen content no greaterthan 25% by weight, preferably below 20% by weight, further preferablybelow 5%. Typically, the oxygen content is between 5% and 20% by weight.The oxygen content can be determined using chemical elemental analysisand/or X-ray photoelectron spectroscopy (XPS).

The laminar graphite materials used in the prior art processes for theproduction of the GIC, graphite oxide, and subsequently made exfoliatedgraphite, flexible graphite sheets, and graphene platelets are, in mostcases, natural graphite. However, the present invention is not limitedto natural graphite. The starting material may be selected from thegroup consisting of natural graphite, artificial graphite (e.g., highlyoriented pyrolytic graphite, HOPG), graphite oxide, graphite fluoride,graphite fiber, carbon fiber, carbon nanofiber, carbon nanotube,mesophase carbon microbead (MCMB) or carbonaceous microsphere (CMS),soft carbon, hard carbon, and combinations thereof. All of thesematerials contain graphite crystallites that are composed of layers ofgraphene planes stacked or bonded together via van der Waals forces. Innatural graphite, multiple stacks of graphene planes, with the grapheneplane orientation varying from stack to stack, are clustered together.In carbon fibers, the graphene planes are usually oriented along apreferred direction. Generally speaking, soft carbons are carbonaceousmaterials obtained from carbonization of liquid-state, aromaticmolecules. Their aromatic ring or graphene structures are more or lessparallel to one another, enabling further graphitization. Hard carbonsare carbonaceous materials obtained from aromatic solid materials (e.g.,polymers, such as phenolic resin and polyfurfuryl alcohol). Theirgraphene structures are relatively randomly oriented and, hence, furthergraphitization is difficult to achieve even at a temperature higher than2,500° C. But, graphene sheets do exist in these carbons.

Graphene sheets may be oxidized to various extents during theirpreparation, resulting in graphite oxide or graphene oxide (GO). Hence,in the present context, graphene preferably or primarily refers to thosegraphene sheets containing no or low oxygen content; but, they caninclude GO of various oxygen contents. Further, graphene may befluorinated to a controlled extent to obtain graphene fluoride.

Pristine graphene may be produced by direct ultrasonication (also knownas liquid phase production) or supercritical fluid exfoliation ofgraphite particles. These processes are well-known in the art. Multiplepristine graphene sheets may be dispersed in water or other liquidmedium with the assistance of a surfactant to form a suspension.

Fluorinated graphene or graphene fluoride is herein used as an exampleof the halogenated graphene material group. There are two differentapproaches that have been followed to produce fluorinated graphene: (1)fluorination of pre-synthesized graphene: This approach entails treatinggraphene prepared by mechanical exfoliation or by CVD growth withfluorinating agent such as XeF₂, or F-based plasmas; (2) Exfoliation ofmultilayered graphite fluorides: Both mechanical exfoliation and liquidphase exfoliation of graphite fluoride can be readily accomplished [F.Karlicky, et al. “Halogenated Graphenes: Rapidly Growing Family ofGraphene Derivatives” ACS Nano, 2013, 7 (8), pp 6434-6464].

Interaction of F₂ with graphite at high temperature leads to covalentgraphite fluorides (CF)_(n) or (C₂F)_(n), while at low temperaturesgraphite intercalation compounds (GIC) C_(x)F (2≤x≤24) form. In (CF)_(n)carbon atoms are sp3-hybridized and thus the fluorocarbon layers arecorrugated consisting of trans-linked cyclohexane chairs. In (C₂F)_(n)only half of the C atoms are fluorinated and every pair of the adjacentcarbon sheets are linked together by covalent C—C bonds. Systematicstudies on the fluorination reaction showed that the resulting F/C ratiois largely dependent on the fluorination temperature, the partialpressure of the fluorine in the fluorinating gas, and physicalcharacteristics of the graphite precursor, including the degree ofgraphitization, particle size, and specific surface area. In addition tofluorine (F₂), other fluorinating agents may be used, although most ofthe available literature involves fluorination with F₂ gas, sometimes inpresence of fluorides.

For exfoliating a layered precursor material to the state of individuallayers or few-layers of graphene planes (hexagonal carbon atom planes),it is necessary to overcome the attractive forces between adjacentlayers and to further stabilize the layers. This may be achieved byeither covalent modification of the graphene surface by functionalgroups or by non-covalent modification using specific solvents,surfactants, polymers, or donor-acceptor aromatic molecules. The processof liquid phase exfoliation includes ultra-sonic treatment of a graphitefluoride in a liquid medium.

The nitrogenation of graphene can be conducted by exposing a graphenematerial, such as graphene oxide, to ammonia at high temperatures(200-400° C.). Nitrogenated graphene could also be formed at lowertemperatures by a hydrothermal method; e.g. by sealing GO and ammonia inan autoclave and then increased the temperature to 150-250° C. Othermethods to synthesize nitrogen doped graphene include nitrogen plasmatreatment on graphene, arc-discharge between graphite electrodes in thepresence of ammonia, ammonolysis of graphene oxide under CVD conditions,and hydrothermal treatment of graphene oxide and urea at differenttemperatures.

In some embodiments, the sulfonated elastomer further contains a lithiumion-conducting additive dispersed therein. The lithium ion-conductingadditive may be selected from Li₂CO₃, Li₂O, Li₂C₂O₄, LiOH, LiX, ROCO₂Li,HCOLi, ROLi, (ROCO₂Li)₂, (CH₂OCO₂Li)₂, Li₂S, Li_(x)SO_(Y), or acombination thereof, wherein X=F, Cl, I, or Br, R=a hydrocarbon group,0<x≤1 and 1≤y≤4.

Alternatively, the lithium ion-conducting additive may contain a lithiumsalt selected from lithium perchlorate (LiClO₄), lithiumhexafluorophosphate (LiPF₆), lithium borofluoride (LiBF₄), lithiumhexafluoroarsenide (LiAsF₆), lithium trifluoro-methanesulfonate(LiCF₃SO₃), bis-trifluoromethyl sulfonylimide lithium (LiN(CF₃SO₂)₂),lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate(LiBF₂C₂O₄), lithium nitrate (LiNO₃), Li-fluoroalkyl-phosphate(LiPF₃(CF₂CF₃)₃), lithium bisperfluoro-ethylsulfonylimide (LiBETI),lithium bis(trifluoromethanesulfonyl)imide, lithiumbis(fluorosulfonyl)imide, lithium trifluoromethanesulfonimide (LiTFSI),an ionic liquid-based lithium salt, or a combination thereof.

In some embodiments, the lithium ion-conducting additive or filler is alithium ion-conducting polymer selected from poly(ethylene oxide) (PEO),polypropylene oxide (PPO), poly(acrylonitrile) (PAN), poly(methylmethacrylate) (PMMA), poly(vinylidene fluoride) (PVdF), poly bis-methoxyethoxyethoxide-phosphazene, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a derivativethereof (e.g. sulfonated versions), or a combination thereof.

The sulfonated elastomer may be mixed with an electron-conductingpolymer selected from polyaniline, polypyrrole, polythiophene,polyfuran, a bi-cyclic polymer, derivatives thereof (e.g. sulfonatedversions), or a combination thereof.

Some elastomers are originally in an unsaturated chemical state(unsaturated rubbers) that can be cured by sulfur vulcanization to forma cross-linked polymer that is highly elastic (hence, an elastomer).Prior to vulcanization, these polymers or oligomers are soluble in anorganic solvent to form a polymer solution. Graphene sheets, as anexample of a conductive additive, can be chemically functionalized tocontain functional groups (e.g. —OH, —COOH, NH₂, etc.) that can reactwith the polymer or its oligomer. The graphene-bonded oligomer orpolymer may then be dispersed in a liquid medium (e.g. a solvent) toform a solution or suspension. Particles of a cathode active material(e.g. LiCoO₂ nanoparticles) can be dispersed in this polymer solution orsuspension to form a slurry of an active material particle-polymermixture. This suspension can then be subjected to a solvent removaltreatment while individual particles remain substantially separated fromone another. The graphene-bonded polymer precipitates out to deposit onsurfaces of these active material particles. This can be accomplished,for instance, via spray drying.

Unsaturated rubbers that can be vulcanized to become elastomer includenatural polyisoprene (e.g. cis-1,4-polyisoprene natural rubber (NR) andtrans-1,4-polyisoprene gutta-percha), synthetic polyisoprene (IR forisoprene rubber), polybutadiene (BR for butadiene rubber), chloroprenerubber (CR), polychloroprene (e.g. Neoprene, Baypren etc.), butyl rubber(copolymer of isobutylene and isoprene, IIR), including halogenatedbutyl rubbers (chloro butyl rubber (CIIR) and bromo butyl rubber (BIIR),styrene-butadiene rubber (copolymer of styrene and butadiene, SBR),nitrile rubber (copolymer of butadiene and acrylonitrile, NBR), Someelastomers are saturated rubbers that cannot be cured by sulfurvulcanization; they are made into a rubbery or elastomeric material viadifferent means: e.g. by having a copolymer domain that holds otherlinear chains together. Graphene sheets or other additives can besolution- or melt-dispersed into the elastomer to form an elastomercomposite. Each of these elastomer composites can be used to encapsulateparticles of an active material by one of several means: melt mixing(followed by pelletizing and ball-milling, for instance), solutionmixing (dissolving the active material particles in an uncured polymer,monomer, or oligomer, with or without an organic solvent) followed bydrying (e.g. spray drying), interfacial polymerization, or in situpolymerization of elastomer in the presence of active materialparticles.

Saturated rubbers and related elastomers in this category include EPM(ethylene propylene rubber, a copolymer of ethylene and propylene), EPDMrubber (ethylene propylene diene rubber, a terpolymer of ethylene,propylene and a diene-component), epichlorohydrin rubber (ECO),polyacrylic rubber (ACM, ABR), silicone rubber (SI, Q, VMQ),fluorosilicone rubber (FVMQ), fluoroelastomers (FKM, and FEPM; such asViton, Tecnoflon, Fluorel, Aflas and Dai-El), perfluoroelastomers (FFKM:Tecnoflon PFR, Kalrez, Chemraz, Perlast), polyether block amides (PEBA),chlorosulfonated polyethylene (CSM; e.g. Hypalon), and ethylene-vinylacetate (EVA), thermoplastic elastomers (TPE), protein resilin, andprotein elastin. Polyurethane and its copolymers (e.g. urea-urethanecopolymer) are particularly useful elastomeric shell materials forencapsulating active material particles.

Several micro-encapsulation processes require the elastomer materials tobe dissolvable in a solvent. Fortunately, all the elastomers used hereinare soluble in some common solvents. Even for those rubbers that are notvery soluble after vulcanization, the un-cured polymer (prior tovulcanization or curing) can be readily dissolved in a common organicsolvent to form a solution. This solution can then be used toencapsulate solid particles via several of the micro-encapsulationmethods to be discussed in what follows. Upon encapsulation, theelastomer shell is then vulcanized or cured. Some examples of rubbersand their solvents are polybutadiene (2-methyl pentane+n-hexane or2,3-dimethylbutane), styrene-butadiene rubber (toluene, benzene, etc.),butyl rubber (n-hexane, toluene, cyclohexane), etc. The SBR can bevulcanized with different amounts of sulfur and accelerator at 433° K inorder to obtain different network structures and crosslink densities.Butyl rubber (IIR) is a copolymer of isobutylene and a small amount ofisoprene (e.g. about 98% polyisobutylene with 2% isoprene distributedrandomly in the polymer chain). Elemental sulfur and organicaccelerators (such as thiuram or thiocarbamates) can be used tocross-link butyl rubber to different extents as desired. Thermoplasticelastomers are also readily soluble in solvents.

There are three broad categories of micro-encapsulation methods that canbe implemented to produce elastomer-encapsulated particles of a cathodeactive material: physical methods, physico-chemical methods, andchemical methods. The physical methods include pan-coating,air-suspension coating, centrifugal extrusion, vibration nozzle, andspray-drying methods. The physico-chemical methods include ionotropicgelation and coacervation-phase separation methods. The chemical methodsinclude interfacial polycondensation, interfacial cross-linking, in-situpolymerization, and matrix polymerization.

Pan-Coating Method:

The pan coating process involves tumbling the active material particlesin a pan or a similar device while the encapsulating material (e.g.elastomer monomer/oligomer, elastomer melt, elastomer/solvent solution)is applied slowly until a desired encapsulating shell thickness isattained.

Air-Suspension Coating Method:

In the air suspension coating process, the solid particles (corematerial) are dispersed into the supporting air stream in anencapsulating chamber. A controlled stream of a polymer-solvent solution(elastomer or its monomer or oligomer dissolved in a solvent; or itsmonomer or oligomer alone in a liquid state) is concurrently introducedinto this chamber, allowing the solution to hit and coat the suspendedparticles. These suspended particles are encapsulated (fully coated)with polymers while the volatile solvent is removed, leaving a very thinlayer of polymer (elastomer or its precursor, which is cured/hardenedsubsequently) on surfaces of these particles. This process may berepeated several times until the required parameters, such asfull-coating thickness (i.e. encapsulating shell or wall thickness), areachieved. The air stream which supports the particles also helps to drythem, and the rate of drying is directly proportional to the temperatureof the air stream, which can be adjusted for optimized shell thickness.

In a preferred mode, the particles in the encapsulating zone portion maybe subjected to re-circulation for repeated coating. Preferably, theencapsulating chamber is arranged such that the particles pass upwardsthrough the encapsulating zone, then are dispersed into slower movingair and sink back to the base of the encapsulating chamber, enablingrepeated passes of the particles through the encapsulating zone untilthe desired encapsulating shell thickness is achieved.

Centrifugal Extrusion:

Active material particles may be encapsulated using a rotating extrusionhead containing concentric nozzles. In this process, a stream of corefluid (slurry containing particles of an active material dispersed in asolvent) is surrounded by a sheath of shell solution or melt. As thedevice rotates and the stream moves through the air it breaks, due toRayleigh instability, into droplets of core, each coated with the shellsolution. While the droplets are in flight, the molten shell may behardened or the solvent may be evaporated from the shell solution. Ifneeded, the capsules can be hardened after formation by catching them ina hardening bath. Since the drops are formed by the breakup of a liquidstream, the process is only suitable for liquid or slurry. A highproduction rate can be achieved. Up to 22.5 kg of microcapsules can beproduced per nozzle per hour and extrusion heads containing 16 nozzlesare readily available.

Vibrational Nozzle Encapsulation Method:

Core-shell encapsulation or matrix-encapsulation of an active materialcan be conducted using a laminar flow through a nozzle and vibration ofthe nozzle or the liquid. The vibration has to be done in resonance withthe Rayleigh instability, leading to very uniform droplets. The liquidcan consist of any liquids with limited viscosities (1-50,000 mPa·s):emulsions, suspensions or slurry containing the active material. Thesolidification can be done according to the used gelation system with aninternal gelation (e.g. sol-gel processing, melt) or an external(additional binder system, e.g. in a slurry).

Spray-Drying:

Spray drying may be used to encapsulate particles of an active materialwhen the active material is dissolved or suspended in a melt or polymersolution. In spray drying, the liquid feed (solution or suspension) isatomized to form droplets which, upon contacts with hot gas, allowsolvent to get vaporized and thin polymer shell to fully embrace thesolid particles of the active material.

Coacervation-Phase Separation:

This process consists of three steps carried out under continuousagitation:

-   (a) Formation of three immiscible chemical phases: liquid    manufacturing vehicle phase, core material phase and encapsulation    material phase. The core material is dispersed in a solution of the    encapsulating polymer (elastomer or its monomer or oligomer). The    encapsulating material phase, which is an immiscible polymer in    liquid state, is formed by (i) changing temperature in polymer    solution, (ii) addition of salt, (iii) addition of non-solvent,    or (iv) addition of an incompatible polymer in the polymer solution.-   (b) Deposition of encapsulation shell material: core material being    dispersed in the encapsulating polymer solution, encapsulating    polymer material coated around core particles, and deposition of    liquid polymer embracing around core particles by polymer adsorbed    at the interface formed between core material and vehicle phase; and-   (c) Hardening of encapsulating shell material: shell material being    immiscible in vehicle phase and made rigid via thermal,    cross-linking, or dissolution techniques.

Interfacial Polycondensation and Interfacial Cross-Linking:

Interfacial polycondensation entails introducing the two reactants tomeet at the interface where they react with each other. This is based onthe concept of the Schotten-Baumann reaction between an acid chlorideand a compound containing an active hydrogen atom (such as an amine oralcohol), polyester, polyurea, polyurethane, or urea-urethanecondensation. Under proper conditions, thin flexible encapsulating shell(wall) forms rapidly at the interface. A solution of the active materialand a diacid chloride are emulsified in water and an aqueous solutioncontaining an amine and a polyfunctional isocyanate is added. A base maybe added to neutralize the acid formed during the reaction. Condensedpolymer shells form instantaneously at the interface of the emulsiondroplets. Interfacial cross-linking is derived from interfacialpolycondensation, wherein cross-linking occurs between growing polymerchains and a multi-functional chemical groups to form an elastomer shellmaterial.

In-Situ Polymerization:

In some micro-encapsulation processes, active materials particles arefully coated with a monomer or oligomer first. Then, directpolymerization of the monomer or oligomer is carried out on the surfacesof these material particles.

Matrix Polymerization:

This method involves dispersing and embedding a core material in apolymeric matrix during formation of the particles. This can beaccomplished via spray-drying, in which the particles are formed byevaporation of the solvent from the matrix material. Another possibleroute is the notion that the solidification of the matrix is caused by achemical change.

A variety of synthetic methods may be used to sulfonate an elastomer orrubber: (i) exposure to sulfur trioxide in vapor phase or in solution,possibly in presence of Lewis bases such as triethyl phosphate,tetrahydrofuran, dioxane, or amines; (ii) chlorosulfonic acid in diethylether; (iii) concentrated sulfuric acid or mixtures of sulfuric acidwith alkyl hypochlorite; (iv) bisulfites combined to dioxygen, hydrogenperoxide, metallic catalysts, or peroxo derivates; and (v) acetylsulfate.

Sulfonation of an elastomer or rubber may be conducted before, during,or after curing of the elastomer or rubber. Further, sulfonation of theelastomer or rubber may be conducted before or after the particles of anelectrode active material are embraced or encapsulated by theelastomer/rubber or its precursor (monomer or oligomer). Sulfonation ofan elastomer or rubber may be accomplished by exposing theelastomer/rubber to a sulfonation agent in a solution state or meltstate, in a batch manner or in a continuous process. The sulfonatingagent may be selected from sulfuric acid, sulfonic acid, sulfurtrioxide, chlorosulfonic acid, a bisulfate, a sulfate (e.g. zincsulfate, acetyl sulfate, etc.), a mixture thereof, or a mixture thereofwith another chemical species (e.g. acetic anhydride, thiolacetic acid,or other types of acids, etc.). In addition to zinc sulfate, there are awide variety of metal sulfates that may be used as a sulfonating agent;e.g. those sulfates containing Mg, Ca, Co, Li, Ba, Na, Pb, Ni, Fe, Mn,K, Hg, Cr, and other transition metals, etc.

For instance, a triblock copolymer, poly(styrene-isobutylene-styrene) orSIBS, may be sulfonated to several different levels ranging from 0.36 to2.04 mequiv./g (13 to 82 mol % of styrene; styrene being 19 mol % of theunsulfonated block copolymer). Sulfonation of SIBS may be performed insolution with acetyl sulfate as the sulfonating agent. First, aceticanhydride reacts with sulfuric acid to form acetyl sulfate (asulfonating agent) and acetic acid (a by-product). Then, excess water isremoved since anhydrous conditions are required for sulfonation of SIBS.The SIBS is then mixed with the mixture of acetyl sulfate and aceticacid. Such a sulfonation reaction produces sulfonic acid substituted tothe para-position of the aromatic ring in the styrene block of thepolymer. Elastomers having an aromatic ring may be sulfonated in asimilar manner.

A sulfonated elastomer also may be synthesized by copolymerization of alow level of functionalized (i.e. sulfonated) monomer with anunsaturated monomer (e.g. olefinic monomer, isoprene monomer oroligomer, butadiene monomer or oligomer, etc.).

Example 1: Sulfonation of Triblock CopolymerPoly(Styrene-Isobutylene-Styrene) or SIBS

An example of the sulfonation procedure used in this study is summarizedas follows: a 10% (w/v) solution of SIBS (50 g) and a desired amount ofgraphene oxide sheets (0.15 TO 405 by wt.) in methylene chloride (500ml) was prepared. The solution was stirred and refluxed at approximately40 8 C, while a specified amount of acetyl sulfate in methylene chloridewas slowly added to begin the sulfonation reaction. Acetyl sulfate inmethylene chloride was prepared prior to this reaction by cooling 150 mlof methylene chloride in an ice bath for approximately 10 min. Aspecified amount of acetic anhydride and sulfuric acid was then added tothe chilled methylene chloride under stirring conditions. Sulfuric acidwas added approximately 10 min after the addition of acetic anhydridewith acetic anhydride in excess of a 1:1 mole ratio. This solution wasthen allowed to return to room temperature before addition to thereaction vessel.

After approximately 5 h, the reaction was terminated by slowly adding100 ml of methanol. The reacted polymer solution was then precipitatedwith deionized water. The precipitate was washed several times withwater and methanol, separately, and then dried in a vacuum oven at 50 8C for 24 h. This washing and drying procedure was repeated until the pHof the wash water was neutral. After this process, the final polymeryield was approximately 98% on average. This sulfonation procedure wasrepeated with different amounts of acetyl sulfate to produce severalsulfonated polymers with various levels of sulfonation or ion-exchangecapacities (IECs). The mol % sulfonation is defined as: mol %=(moles ofsulfonic acid/moles of styrene)×100%, and the IEC is defined as themille-equivalents of sulfonic acid per gram of polymer (mequiv./g).

After sulfonation and washing of each polymer, the S—SIBS samples weredissolved in a mixed solvent of toluene/hexanol (85/15, w/w) to formsolutions having polymer concentrations ranging from 5 to 2.5% (w/v).Particles of a desired cathode active material, along with a desiredamount of conducting additive (e.g. graphene sheets or CNTs) were thenadded into the polymer solution samples to obtain slurry samples. Theslurry samples were separately spray-dried to form sulfonatedelastomer-embraced particles.

Alternatively, sulfonation may be conducted on the sulfonated elastomerlayer after this encapsulating layer is form (e.g. after the activematerial particle(s) is/are encapsulated.

Example 2: Synthesis of Sulfonated Polybutadiene (PB) by Free RadicalAddition of Thiolacetic Acid (TAA) Followed by In Situ Oxidation withPerformic Acid

A representative procedure is given as follows. PB (8.0 g) was dissolvedin toluene (800 mL) under vigorous stirring for 72 h at room temperaturein a 1 L round-bottom flask. Benzophenone (BZP) (0.225 g; 1.23 mmol;BZP/olefin molar ratio=1:120) and TAA (11.9 mL; 0.163 mol, TAA/olefinmolar ratio=1.1) were introduced into the reactor, and the polymersolution was irradiated for 1 h at room temperature with UV light of 365nm and power of 100 W.

The resulting thioacetylated polybutadiene (PB-TA) was isolated bypouring 200 mL of the toluene solution in a plenty of methanol and thepolymer recovered by filtration, washed with fresh methanol, and driedin vacuum at room temperature (Yield=3.54 g). Formic acid (117 mL; 3.06mol; HCOOH/olefin molar ratio=25), along with a desired amount ofcathode active material particles, from 10 to 100 grams) were added tothe toluene solution of PB-TA at 50° C. followed by slow addition of52.6 mL of hydrogen peroxide (35 wt %; 0.61 mol; H₂O₂/olefin molarratio=5) in 20 min. We would like to caution that the reaction isautocatalytic and strongly exothermic. The resulting slurry wasspray-dried to obtain reinforced sulfonated polybutadiene(PB-SA-encapsulated cathode active material particles.

Example 3: Synthesis of Sulfonated SBS

Sulfonated styrene-butadiene-styrene triblock copolymer (SBS) basedelastomer was directly synthesized. First, SBS (optionally along withgraphene sheets) is first epoxidized by performic acid formed in situ,followed by ring-opening reaction with an aqueous solution of NaHSO₃. Ina typical procedure, epoxidation of SBS was carried out via reaction ofSBS in cyclohexane solution (SBS concentration=11 g/100 mL) withperformic acid formed in situ from HCOOH and 30% aqueous H₂O₂ solutionat 70° C. for 4 h, using 1 wt % poly(ethylene glycol)/SBS as a phasetransfer catalyst. The molar ratio of H₂O₂/HCOOH was 1. The product(ESBS) was precipitated and washed several times with ethanol, followedby drying in a vacuum dryer at 60° C.

Subsequently, ESBS was first dissolved in toluene to form a solutionwith a concentration of 10 g/100 mL, into which was added 5 wt %TEAB/ESBS as a phase transfer catalyst and 5 wt % DMA/ESBS as aring-opening catalyst. Herein, TEAB=tetraethyl ammonium bromide andDMA=N,N-dimethyl aniline. An aqueous solution of NaHSO₃ and Na₂SO₃(optionally along with graphene sheets or other desired additives, ifnot added earlier) was then added with vigorous stirring at 60° C. for 7h at a molar ratio of NaHSO₃/epoxy group at 1.8 and a weight ratio ofNa₂SO₃/NaHSO₃ at 36%. This reaction allows for opening of the epoxidering and attaching of the sulfonate group according to the followingreaction:

The reaction was terminated by adding a small amount of acetone solutioncontaining antioxidant. The mixture was washed with distilled waterthree times, then precipitated by ethanol, followed by drying in avacuum dryer at 50° C. It may be noted that particles of an electrodeactive material may be added during various stages of the aforementionedprocedure (e.g. right from the beginning, or prior to the ring openingreaction). Preferably, the optional electron-conducting additive orlithium ion-conducting additive is added before or during the ringopening reaction and the cathode active material is added afterwards.

Example 4: Synthesis of Sulfonated SBS by Free Radical Addition ofThiolacetic Acid (TAA) Followed by In Situ Oxidation with Performic Acid

A representative procedure is given as follows. SBS (8.000 g) in toluene(800 mL) was left under vigorous stirring for 72 hours at roomtemperature and heated later on for 1 h at 65° C. in a 1 L round-bottomflask until the complete dissolution of the polymer. Thus, benzophenone(BZP, 0.173 g; 0.950 mmol; BZP/olefin molar ratio=1:132) and TAA (8.02mL; 0.114 mol, TAA/olefin molar ratio=1.1) were added, and the polymersolution was irradiated for 4 h at room temperature with UV light of 365nm and power of 100 W. To isolate a fraction of the thioacetylatedsample, 20 mL of the polymer solution was treated with plenty ofmethanol, and the polymer was recovered by filtration, washed with freshmethanol, and dried in vacuum at room temperature. The toluene solutioncontaining the thioacetylated polymer was equilibrated at 50° C., and107.4 mL of formic acid (2.84 mol; HCOOH/olefin molar ratio=27.5) and48.9 mL of hydrogen peroxide (35 wt %; 0.57 mol; H₂O₂/olefin molarratio=5.5) were added in about 15 min. It may be cautioned that thereaction is autocatalytic and strongly exothermic!Particles of thedesired cathode active materials were added before or after thisreaction. The resulting slurry was stirred for 1 h, and then most of thesolvent was distilled off in vacuum at 35° C. Finally, the slurrycontaining the sulfonated elastomer was coagulated in a plenty ofacetonitrile, isolated by filtration, washed with fresh acetonitrile,and dried in vacuum at 35° C. to obtain sulfonated elastomers.

Other elastomers (e.g. polyisoprene, EPDM, EPR, polyurethane, etc.) weresulfonated in a similar manner. Alternatively, all the rubbers orelastomers can be directly immersed in a solution of sulfuric acid, amixture of sulfuric acid and acetyl sulfate, or other sulfonating agentdiscussed above to produce sulfonated elastomers/rubbers. Again, cathodeactive material particles may be added at various stages of theprocedure.

Example 5: Graphene Oxide from Sulfuric Acid Intercalation andExfoliation of MCMBs

MCMB (mesocarbon microbeads) were supplied by China Steel Chemical Co.This material has a density of about 2.24 g/cm³ with a median particlesize of about 16 μm. MCMBs (10 grams) were intercalated with an acidsolution (sulfuric acid, nitric acid, and potassium permanganate at aratio of 4:1:0.05) for 48 hours. Upon completion of the reaction, themixture was poured into deionized water and filtered. The intercalatedMCMBs were repeatedly washed in a 5% solution of HCl to remove most ofthe sulfate ions. The sample was then washed repeatedly with deionizedwater until the pH of the filtrate was neutral. The slurry was dried andstored in a vacuum oven at 60° C. for 24 hours. The dried powder samplewas placed in a quartz tube and inserted into a horizontal tube furnacepre-set at a desired temperature, 800° C.-1,100° C. for 30-90 seconds toobtain graphene samples. A small quantity of graphene was mixed withwater and ultrasonicated at 60-W power for 10 minutes to obtain asuspension. A small amount was sampled out, dried, and investigated withTEM, which indicated that most of the NGPs were between 1 and 10 layers.The oxygen content of the graphene powders (GO or RGO) produced was from0.1% to approximately 25%, depending upon the exfoliation temperatureand time.

Example 6: Oxidation and Exfoliation of Natural Graphite

Graphite oxide was prepared by oxidation of graphite flakes withsulfuric acid, sodium nitrate, and potassium permanganate at a ratio of4:1:0.05 at 30° C. for 48 hours, according to the method of Hummers[U.S. Pat. No. 2,798,878, Jul. 9, 1957]. Upon completion of thereaction, the mixture was poured into deionized water and filtered. Thesample was then washed with 5% HCl solution to remove most of thesulfate ions and residual salt and then repeatedly rinsed with deionizedwater until the pH of the filtrate was approximately 4. The intent wasto remove all sulfuric and nitric acid residue out of graphiteinterstices. The slurry was dried and stored in a vacuum oven at 60° C.for 24 hours.

The dried, intercalated (oxidized) compound was exfoliated by placingthe sample in a quartz tube that was inserted into a horizontal tubefurnace pre-set at 1,050° C. to obtain highly exfoliated graphite. Theexfoliated graphite was dispersed in water along with a 1% surfactant at45° C. in a flat-bottomed flask and the resulting graphene oxide (GO)suspension was subjected to ultrasonication for a period of 15 minutesto obtain a homogeneous graphene-water suspension.

Example 7: Preparation of Pristine Graphene Sheets

Pristine graphene sheets were produced by using the directultrasonication or liquid-phase exfoliation process. In a typicalprocedure, five grams of graphite flakes, ground to approximately 20 μmin sizes, were dispersed in 1,000 mL of deionized water (containing 0.1%by weight of a dispersing agent, Zonyl® FSO from DuPont) to obtain asuspension. An ultrasonic energy level of 85 W (Branson S450Ultrasonicator) was used for exfoliation, separation, and size reductionof graphene sheets for a period of 15 minutes to 2 hours. The resultinggraphene sheets were pristine graphene that had never been oxidized andwere oxygen-free and relatively defect-free. There are substantially noother non-carbon elements.

Example 8: Preparation of Graphene Fluoride (GF) Sheets

Several processes have been used by us to produce GF, but only oneprocess is herein described as an example. In a typical procedure,highly exfoliated graphite (HEG) was prepared from intercalated compoundC₂F.xClF₃. HEG was further fluorinated by vapors of chlorine trifluorideto yield fluorinated highly exfoliated graphite (FHEG). A pre-cooledTeflon reactor was filled with 20-30 mL of liquid pre-cooled ClF₃, andthen the reactor was closed and cooled to liquid nitrogen temperature.Subsequently, no more than 1 g of HEG was put in a container with holesfor ClF₃ gas to access the reactor. After 7-10 days, a gray-beigeproduct with approximate formula C₂F was formed. GF sheets were thendispersed in halogenated solvents to form suspensions.

Example 9: Preparation of Nitrogenated Graphene Sheets

Graphene oxide (GO), synthesized in Example 12, was finely ground withdifferent proportions of urea and the pelletized mixture heated in amicrowave reactor (900 W) for 30 s. The product was washed several timeswith deionized water and vacuum dried. In this method graphene oxidegets simultaneously reduced and doped with nitrogen. The productsobtained with graphene/urea mass ratios of 1/0.5, 1/1 and 1/2 aredesignated as N-1, N-2 and N-3 respectively and the nitrogen contents ofthese samples were 14.7, 18.2 and 17.5 wt. % respectively as determinedby elemental analysis. These nitrogenated graphene sheets remaindispersible in water.

Example 10: Cathode Particulates Containing V₂O₅ Particles Encapsulatedby a Shell of Sulfonated Elastomer

Cathode active material layers were prepared from V₂O₅ particles andgraphene-embraced V₂O₅ particles, respectively. V₂O₅ particles werecommercially available. Graphene-embraced V₂O₅ particles were preparedin-house. In a typical experiment, vanadium pentoxide gels were obtainedby mixing V₂O₅ in a LiCl aqueous solution. The Li⁺-exchanged gelsobtained by interaction with LiCl solution (the Li:V molar ratio waskept as 1:1) was mixed with a GO suspension and then placed in aTeflon-lined stainless steel 35 ml autoclave, sealed, and heated up to180° C. for 12 h. After such a hydrothermal treatment, the green solidswere collected, thoroughly washed, ultrasonicated for 2 minutes, anddried at 70° C. for 12 h followed by mixing with another 0.1% GO inwater, ultrasonicating to break down nanobelt sizes, and thenspray-drying at 200° C. to obtain graphene-embraced V₂O₅ compositeparticulates.

For electrochemical testing, the working electrodes were prepared bymixing 85 wt. % active material (sulfonated elastomer encapsulated ornon-encapsulated particulates of V₂O₅, respectively), 7 wt. % acetyleneblack (Super-P), and 8 wt. % polyvinylidene fluoride (PVDF) binderdissolved in N-methyl-2-pyrrolidinoe (NMP) to form a slurry of 5 wt. %total solid content. After coating the slurries on Al foil, theelectrodes were dried at 120° C. in vacuum for 2 h to remove the solventbefore pressing. Then, the electrodes were cut into a disk (4=12 mm) anddried at 100° C. for 24 h in vacuum. Electrochemical measurements werecarried out using CR2032 (3V) coin-type cells with lithium metal as thecounter/reference electrode, Celgard 2400 membrane as separator, and 1 MLiPF₆ electrolyte solution dissolved in a mixture of ethylene carbonate(EC) and diethyl carbonate (DEC) (EC-DEC, 1:1 v/v). The cell assemblywas performed in an argon-filled glove-box. The CV measurements werecarried out using a CH-6 electrochemical workstation at a scanning rateof 1 mV/s.

The electrochemical performance of the particulates of sulfonatedelastomer-encapsulated V₂O₅ particles and that of non-protected V₂O₅were evaluated by galvanostatic charge/discharge cycling at a currentdensity of 50 mA/g, using a LAND electrochemical workstation.

Summarized in FIG. 3 are the specific intercalation capacity curves offour lithium cells: cathode containing un-encapsulated V₂O₅ particles,cathode containing un-encapsulated but graphene-embraced V₂O₅ particles,cathode containing sulfonated elastomer-encapsulated V₂O₅ particles, andcathode containing sulfonated elastomer-encapsulated graphene-embracedV₂O₅ particles. As the number of cycles increases, the specific capacityof the un-encapsulated V₂O₅ electrode drops at the fastest rate. Incontrast, the presently invented sulfonated elastomer encapsulationprovides the battery cell with a significantly more stable and higherspecific capacity for a large number of cycles. These data have clearlydemonstrated the surprising and superior performance of the presentlyinvented sulfonated elastomer encapsulation approach.

The protecting sulfonated elastomer encapsulation shell appears to becapable of reversibly deforming to a great extent without breakage whenthe active material particles expand and shrink. The sulfonatedelastomer also remains chemically bonded to the binder resin when theencapsulated particles expand or shrink. In contrast, the PVDF binder isbroken or detached from some of the non-encapsulated active materialparticles. These were observed by using SEM to examine the surfaces ofthe electrodes recovered from the battery cells after some numbers ofcharge-discharge cycles.

Example 11: Sulfonated Elastomer-Encapsulated Lithium Iron Phosphate(LFP) Particles

Commercially available lithium iron phosphate (LFP) particles were usedin the present study. The battery cells from the sulfonatedelastomer-encapsulated LFP particles and non-coated LFP particles wereprepared using a procedure described in Example 1. FIG. 4 shows that thecathode prepared according to the presently invented sulfonatedelastomer-encapsulated particulate approach offers a significantly morestable and higher reversible capacity compared to the un-coated LFPparticle-based. The sulfonated elastomer is more capable of holding theactive material particles and conductive additive together,significantly improving the structural integrity of the active materialelectrode. The sulfonated elastomer also acts to isolate the electrolytefrom the active material yet still allowing for easy diffusion oflithium ions.

Example 12: Metal Fluoride and Metal Chloride Particles Encapsulated bya Sulfonated Styrene-Butadiene Rubber (SBR)/Graphene Composite

Commercially available powders of CoF₃, MnF₃, FeF₃, VF₃, VOF₃, TiF₃, andBiF₃ were subjected to high-intensity ball-milling to reduce theparticle size down to approximately 0.5-2.3 μm. Each type of these metalfluoride particles, along with graphene sheets (as a conductiveadditive), were encapsulated with a thin layer of sulfonated SBR shell(prepared in Example 3) via the spray-drying method, followed by curingof the butadiene segment of the SBR chains to impart high elasticity tothe SBR. For comparison, some amount of FeF₃ nanoparticles wasencapsulated by a carbon shell. Carbon encapsulation is well-known inthe art. Un-protected FeF₃ nanoparticles from the same batch were alsoinvestigated to determine and compare the cycling behaviors of thelithium-ion batteries containing these particles as the cathode activematerial.

Shown in FIG. 5 are the discharge capacity curves of two coin cellshaving two different types of cathode active materials: (1) sulfonatedelastomer-encapsulated metal fluoride particles and (2) non-encapsulatedmetal fluorides. These results have clearly demonstrated that thesulfonated elastomer encapsulation strategy provides excellentprotection against capacity decay of a lithium metal battery featuring ahigh-capacity cathode active material.

The high-elasticity sulfonated elastomer appears to be capable ofreversibly deforming without breakage when the cathode active materialparticles expand and shrink. The elastomer also remains chemicallybonded to the binder resin when the active particles expand or shrink.In contrast, both SBR (as a binder, not an encapsulating shell) andPVDF, the two conventional binder resins, are broken or detached fromsome of the non-encapsulated active material particles. The sulfonatedelastomer has contributed to the structural stability of the electrodelayer. These were observed by using SEM to examine the surfaces of theelectrodes recovered from the battery cells after some numbers ofcharge-discharge cycles.

Example 13: Metal Naphthalocyanine-Reduced Graphene Oxide (FePc/RGO)Hybrid Particulates Encapsulated by a Sulfonated Elastomer

Particles of combined FePc/graphene sheets were obtained by ball-millinga mixture of FePc and RGO in a milling chamber for 30 minutes. Theresulting FePc/RGO mixture particles were potato-like in shape. Some ofthese mixture particles were encapsulated by a high-elasticity elastomerusing the pan-coating procedure. Two lithium cells were prepared, eachcontaining a Li foil anode, a porous separator, and a cathode layer ofFePc/RGO particles (encapsulated or un-encapsulated).

The cycling behaviors of these 2 lithium cells are shown in FIG. 6,which indicates that the lithium-organic cell having a sulfonatedelastomer-encapsulated particulates in the cathode layer exhibits asignificantly more stable cycling response. This encapsulation elastomerreduces or eliminates direct contact between the catalytic transitionmetal element (Fe) and the electrolyte, yet still being permeable tolithium ions. This elastomer shell also completely eliminates thedissolution of naphthalocyanine compounds in the liquid electrolyte.This approach has significantly increased the cycle life of alllithium-organic batteries.

Example 14: Effect of Lithium Ion-Conducting Additive in an ElastomerShell

A wide variety of lithium ion-conducting additives were added to severaldifferent sulfonated elastomer materials to prepare encapsulation shellmaterials for protecting core particles of active material. We havediscovered that these elastomer materials are suitable encapsulationshell materials provided that their lithium ion conductivity at roomtemperature is no less than 10⁻⁷ S/cm. With these materials, lithiumions appear to be capable of readily diffusing in and out of theencapsulation shell having a thickness no greater than 1 μm. For thickershells (e.g. 10 μm), a lithium ion conductivity at room temperature noless than 10⁻⁴ S/cm would be required.

TABLE 1 Lithium ion conductivity of various sulfonated elastomercomposite compositions as a shell material for protecting activematerial particles. Lithium- Sample conducting Sulfonated elastomerLi-ion No. additive (0.3-2 μm thick) conductivity (S/cm) E-1s Li₂CO₃ +70-99% polyurethane, 5.8 × 10⁻⁶ to (CH₂OCO₂Li)₂ 2% RGO 5.6 × 10⁻³ S/cmE-2s Li₂CO₃ + 65-99% polyisoprene, 2.6 × 10⁻⁵ to (CH₂OCO₂Li)₂ 8%pristine graphene 8.5 × 10⁻⁴ S/cm E-3s Li₂CO₃ + 65-80% SBR, 15% 9.3 ×10⁻⁶ to (CH₂OCO₂Li)₂ RGO 9.7 × 10⁻⁴ S/cm D-4s Li₂CO₃ + 70-99%urethane-urea, 2.4 × 10⁻⁶ to (CH₂OCO₂Li)₂ 12% nitrogenated 6.8 × 10⁻⁴S/cm graphene D-5s Li₂CO₃ + 75-99% polybutadiene 2.4 × 10⁻⁵ to(CH₂OCO₂Li)₂ 8.8 × 10⁻³ S/cm B1s LiF + LiOH + 80-99% chloroprene 2.4 ×10⁻⁶ to Li₂C₂O₄ rubber 7.7 × 10⁻⁴ S/cm B2s LiF + HCOLi 80-99% EPDM 6.6 ×10⁻⁶ to 6.1 × 10⁻³ S/cm B3s LiOH 70-99% polyurethane 4.6 × 10⁻⁵ to 4.8 ×10⁻³ S/cm B4s Li₂CO₃ 70-99% polyurethane 5.8 × 10⁻⁵ to 5.7 × 10⁻³ S/cmB5s Li₂C₂O₄ 70-99% polyurethane 2.7 × 10⁻⁵ to 3.7 × 10⁻³ S/cm B6sLi₂CO₃ + LiOH 70-99% polyurethane 2.9 × 10⁻⁵ to 4.7 × 10⁻³ S/cm C1sLiClO₄ 70-99% urethane-urea 6.3 × 10⁻⁵ to 5.4 × 10⁻³ S/cm C2s LiPF₆70-99% urethane-urea 5.4 × 10⁻⁵ to 2.6 × 10⁻³ S/cm C3s LiBF₄ 70-99%urethane-urea 3.6 × 10⁻⁵ to 4.8 × 10⁻⁴ S/cm C4s LiBOB + LiNO₃ 70-99%urethane-urea 9.7 × 10⁻⁶ to 4.2 × 10⁻⁴ S/cm S1s Sulfonated 85-99% SBR8.6 × 10⁻⁶ to polyaniline 9.8 × 10⁻⁴ S/cm S2s Sulfonated SBR 85-99% SBR8.6 × 10⁻⁶ to 6.3 × 10⁻⁴ S/cm S3s Sulfonated 80-99% chlorosulfonated 5.8× 10⁻⁶ to PVDF polyethylene (CS-PE) 6.4 × 10⁻⁴ S/cm S4s Polyethylene80-99% CS-PE 6.9 × 10⁻⁶ to oxide 5.4 × 10⁻⁴ S/cm

Some advantages of the present invention may be summarized in thefollowing:

-   -   (1) The sulfonated elastomer encapsulation strategy is        surprisingly effective in alleviating the cathode        expansion/shrinkage-induced capacity decay problems.    -   (2) The encapsulation of high-capacity cathode active material        particles by carbon or other non-elastomeric protective        materials does not provide much benefit in terms of improving        cycling stability of a lithium-ion battery    -   (3) Sulfonation improves the lithium ion conductivity of an        elastomer and, hence, power density of the resulting battery.    -   (4) This encapsulation elastomer strategy reduces or eliminates        direct contact between the catalytic transition metal element        (e.g. Fe, Mn, Ni, Co, etc.) commonly used in a cathode active        material and the electrolyte, thereby reducing/eliminating        catalytic decomposition of the electrolyte.

We claim:
 1. A cathode electrode for a lithium battery, said cathodeelectrode comprising multiple particulates of a cathode active material,wherein at least one of said particulates comprises one or a pluralityof particles of a cathode active material being encapsulated by a thinlayer of a sulfonated elastomeric material that has a fully recoverabletensile strain from 2% to 800%, a lithium ion conductivity from 10⁻⁷S/cm to 5×10⁻² S/cm at room temperature, and an encapsulating shellthickness from 1 nm to 10 μm.
 2. The cathode electrode of claim 1,wherein said sulfonated elastomeric material comprises a materialselected from the group consisting of sulfonated natural polyisoprene,sulfonated synthetic polyisoprene, sulfonated polybutadiene, sulfonatedchloroprene rubber, sulfonated polychloroprene, sulfonated butyl rubber,sulfonated styrene-butadiene rubber, sulfonated nitrile rubber,sulfonated ethylene propylene rubber, sulfonated ethylene propylenediene rubber, sulfonated metallocene-based poly(ethylene-co-octene)(POE) elastomer, sulfonated poly(ethylene-co-butene) (PBE) elastomer,sulfonated styrene-ethylene-butadiene-styrene (SEBS) elastomer,sulfonated epichlorohydrin rubber, sulfonated polyacrylic rubber,sulfonated silicone rubber, sulfonated fluorosilicone rubber, sulfonatedperfluoroelastomers, sulfonated polyether block amides, sulfonatedchlorosulfonated polyethylene, sulfonated ethylene-vinyl acetatepolymer, sulfonated thermoplastic elastomer, sulfonated protein resilin,sulfonated protein elastin, sulfonated ethylene oxide-epichlorohydrincopolymer, sulfonated polyurethane, sulfonated urethane-urea copolymer,and combinations thereof.
 3. The cathode electrode of claim 1, whereinsaid sulfonated elastomeric material further comprises anelectron-conducting filler dispersed in said elastomeric materialwherein said electron-conducting filler is selected from the groupconsisting of carbon nanotube, carbon nanofiber, nanocarbon particle,metal nanoparticle, metal nanowire, electron-conducting polymer,graphene, and combinations thereof, wherein said graphene is selectedfrom pristine graphene, graphene oxide, reduced graphene oxide, graphenefluoride, graphene chloride, nitrogenated graphene, hydrogenatedgraphene, doped graphene, functionalized graphene, or a combinationthereof.
 4. The cathode electrode of claim 3, wherein saidelectron-conducting polymer is selected from polyaniline, polypyrrole,polythiophene, polyfuran, a bi-cyclic polymer, a sulfonated derivativethereof, or a combination thereof.
 5. The cathode electrode of claim 1,wherein said cathode active material is selected from an inorganicmaterial, an organic material, a polymeric material, or a combinationthereof.
 6. The cathode electrode of claim 5, wherein said inorganicmaterial is selected from a metal oxide, metal phosphate, metalsilicide, metal selenide, transition metal sulfide, sulfur, lithiumpolysulfide, selenium, lithium selenide, or a combination thereof. 7.The cathode electrode of claim 5, wherein said inorganic material isselected from the group consisting of lithium cobalt oxide, lithiumnickel oxide, lithium manganese oxide, lithium vanadium oxide,lithium-mixed metal oxide, lithium iron phosphate, lithium manganesephosphate, lithium vanadium phosphate, lithium mixed metal phosphate,lithium metal silicide, and combinations thereof.
 8. The cathodeelectrode of claim 5, wherein said inorganic material is selected fromthe group consisting of metal fluoride or metal chloride including thegroup consisting of CoF₃, MnF₃, FeF₃, VF₃, VOF₃, TiF₃, BiF₃, NiF₂, FeF₂,CuF₂, CuF, SnF₂, AgF, CuCl₂, FeCl₃, MnCl₂, and combinations thereof. 9.The cathode electrode of claim 5, wherein said inorganic material isselected from a lithium transition metal silicate, denoted as Li₂MSiO₄or Li₂Ma_(x)Mb_(y)SiO₄, wherein M and Ma are selected from Fe, Mn, Co,Ni, V, or VO; Mb is selected from Fe, Mn, Co, Ni, V, Ti, Al, B, Sn, orBi; and x+y≤1.
 10. The cathode electrode of claim 5, wherein saidinorganic material is selected from a transition metal dichalcogenide, atransition metal trichalcogenide, or a combination thereof.
 11. Thecathode electrode of claim 5, wherein said inorganic material isselected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, COO₂, an iron oxide, avanadium oxide, or a combination thereof.
 12. The cathode electrode ofclaim 6, wherein said metal oxide comprises a vanadium oxide selectedfrom the group consisting of VO₂, Li_(x)VO₂, V₂O₅, Li_(x)V₂O₅, V₃O₈,Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉, Li_(x)V₄O₉, V₆O₁₃, Li_(x)V₆O₁₃, theirdoped versions, their derivatives, and combinations thereof, wherein0.1<x<5.
 13. The cathode electrode of claim 6, wherein said metal oxideor metal phosphate is selected from a layered compound LiMO₂, spinelcompound LiM₂O₄, olivine compound LiMPO₄, silicate compound Li₂MSiO₄,tavorite compound LiMPO₄F, borate compound LiMBO₃, or a combinationthereof, wherein M is a transition metal or a mixture of multipletransition metals.
 14. The cathode electrode of claim 5, wherein saidinorganic material is selected from: (a) bismuth selenide or bismuthtelluride, (b) transition metal dichalcogenide or trichalcogenide, (c)sulfide, selenide, or telluride of niobium, zirconium, molybdenum,hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel,or a transition metal; (d) boron nitride, or (e) a combination thereof.15. The cathode electrode of claim 5, wherein said organic material orpolymeric material is selected from the group consisting ofpoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, quino(triazene), redox-active organic material,tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenyl ene (HMTP),poly(5-amino-1,4-dyhydroxy anthraquinone) (PADAQ), phosphazene disulfidepolymer ([(NPS₂)₃]n), lithiated 1,4,5,8-naphthalenetetraol formaldehydepolymer, hexaazatrinaphtylene (HATN), hexaazatriphenylenehexacarbonitrile (HAT(CN)₆), 5-benzylidene hydantoin, isatine lithiumsalt, pyromellitic diimide lithium salt, tetrahydroxy-p-benzoquinonederivatives (THQLi₄), N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, and combinations thereof.
 16. The cathode electrode ofclaim 15, wherein said thioether polymer is selected from the groupconsisting of poly[methanetetryl-tetra(thiomethylene)] (PMTTM),poly(2,4-dithiopentanylene) (PDTP), a polymer containingpoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, poly(2-phenyl-1,3-dithiolane) (PPDT),poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene](PTKPTB, andpoly[3,4(ethylenedithio)thiophene] (PEDTT).
 17. The cathode electrode ofclaim 5, wherein said organic material contains a phthalocyaninecompound selected from the group consisting of copper phthalocyanine,zinc phthalocyanine, tin phthalocyanine, iron phthalocyanine, leadphthalocyanine, nickel phthalocyanine, vanadyl phthalocyanine,fluorochromium phthalocyanine, magnesium phthalocyanine, manganousphthalocyanine, dilithium phthalocyanine, aluminum phthalocyaninechloride, cadmium phthalocyanine, chlorogallium phthalocyanine, cobaltphthalocyanine, silver phthalocyanine, a metal-free phthalocyanine, achemical derivative thereof, and combination thereof.
 18. The cathodeelectrode of claim 1, wherein said cathode active material is in a formof nanoparticle, nanowire, nanofiber, nanotube, nanosheet, nanobelt,nanoribbon, nanodisc, nanoplatelet, or nanohorn having a thickness ordiameter from 0.5 nm to 100 nm.
 19. The cathode electrode of claim 1,wherein said one or a plurality of particles is coated with a layer ofcarbon prior to being encapsulated.
 20. The cathode electrode of claim1, wherein said particulate further comprises a graphite or carbonmaterial encapsulated therein.
 21. The cathode electrode of claim 20,wherein said graphite or carbon material is selected from the groupconsisting of polymeric carbon, amorphous carbon, chemical vapordeposition carbon, coal tar pitch, petroleum pitch, mesophase pitch,carbon black, coke, acetylene black, activated carbon, fine expandedgraphite particle with a dimension smaller than 100 nm, artificialgraphite particle, natural graphite particle, and combinations thereof.22. The cathode electrode of claim 1, wherein said sulfonatedelastomeric material further contains from 0.1% to 40% by weight of alithium ion-conducting additive dispersed in said sulfonated elastomericmaterial.
 23. The cathode electrode of claim 22, wherein said lithiumion-conducting additive is selected from Li₂CO₃, Li₂O, Li₂C₂O₄, LiOH,LiX, ROCO₂Li, HCOLi, ROLi, (ROCO₂Li)₂, (CH₂OCO₂Li)₂, Li₂S, Li_(x)SO_(y),or a combination thereof, wherein X=F, Cl, I, or Br, R=a hydrocarbongroup, 0<x≤1 and 1≤y≤4.
 24. The cathode electrode of claim 22, whereinsaid lithium ion-conducting additive contains a lithium salt selectedfrom lithium perchlorate (LiClO₄), lithium hexafluorophosphate (LiPF₆),lithium borofluoride (LiBF₄), lithium hexafluoroarsenide (LiAsF₆),lithium trifluoro-methanesulfonate (LiCF₃SO₃), bis-trifluoromethylsulfonylimide lithium (LiN(CF₃SO₂)₂), lithium bis(oxalato)borate(LiBOB), lithium oxalyldifluoroborate (LiBF₂C₂O₄), lithium nitrate(LiNO₃), Li-fluoroalkyl-phosphate (LiPF₃(CF₂CF₃)₃), lithiumbisperfluoro-ethylsulfonylimide (LiBETI), lithiumbis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide,lithium trifluoromethanesulfonimide (LiTFSI), an ionic liquid-basedlithium salt, or a combination thereof.
 25. The cathode electrode ofclaim 22, wherein said lithium ion-conducting additive contains alithium ion-conducting polymer is selected from the group consisting ofpoly(ethylene oxide) (PEO), polypropylene oxide (PPO),poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA),poly(vinylidene fluoride) (PVDF), poly bis-methoxyethoxyethoxide-phosphazene, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, and combinations thereof.
 26. A powder mass of acathode active material for a lithium battery cathode electrode, saidpowder mass comprising multiple particulates of a cathode activematerial, wherein at least one of said particulates comprises one or aplurality of particles of said cathode active material beingencapsulated by a thin layer of a sulfonated elastomeric material,wherein said encapsulating thin layer of sulfonated elastomeric materialhas a thickness from 1 nm to 10 μm, a fully recoverable tensile strainfrom 2% to 800%, and a lithium ion conductivity from 10⁻⁷ S/cm to 5×10⁻²S/cm.
 27. The powder mass of claim 26, wherein said sulfonatedelastomeric material comprises a material selected from the groupconsisting of natural polyisoprene, synthetic polyisoprene,polybutadiene, chloroprene rubber, polychloroprene, butyl rubber,styrene-butadiene rubber, nitrile rubber, ethylene propylene rubber,ethylene propylene diene rubber, metallocene-basedpoly(ethylene-co-octene) elastomer, poly(ethylene-co-butene) elastomer,styrene-ethylene-butadiene-styrene elastomer, epichlorohydrin rubber,polyacrylic rubber, silicone rubber, fluorosilicone rubber,perfluoroelastomers, polyether block amides, chlorosulfonatedpolyethylene, ethylene-vinyl acetate, thermoplastic elastomer, proteinresilin, protein elastin, ethylene oxide-epichlorohydrin copolymer,polyurethane, urethane-urea copolymer, sulfonated versions thereof, andcombinations thereof.
 28. The powder mass of claim 26, wherein saidsulfonated elastomeric material further comprises an electron-conductingfiller dispersed in said sulfonated elastomeric material wherein saidelectron-conducting filler is selected from a carbon nanotube, carbonnanofiber, nanocarbon particle, metal nanoparticle, metal nanowire,electron-conducting polymer, graphene, or a combination thereof, whereinsaid graphene is selected from pristine graphene, graphene oxide,reduced graphene oxide, graphene fluoride, graphene chloride,nitrogenated graphene, hydrogenated graphene, doped graphene,functionalized graphene, or a combination thereof and said graphenecomprises single-layer graphene or few-layer graphene, wherein saidfew-layer graphene is defined as a graphene platelet formed of less than10 graphene planes.
 29. The powder mass of claim 26, further comprisinggraphite particles, carbon particles, mesophase microbeads, carbon orgraphite fibers, carbon nanotubes, graphene sheets, or a combinationthereof mixed with said multiple particulates.
 30. The powder mass ofclaim 26, wherein said sulfonated elastomeric material further containsfrom 0.1% to 40% by weight of a lithium ion-conducting additivedispersed in said sulfonated elastomeric material.
 31. The powder massof claim 30, wherein said lithium ion-conducting additive is selectedfrom Li₂CO₃, Li₂O, Li₂C₂O₄, LiOH, LiX, ROCO₂Li, HCOLi, ROLi, (ROCO₂Li)₂,(CH₂OCO₂Li)₂, Li₂S, Li_(x)SO_(Y), or a combination thereof, wherein X=F,Cl, I, or Br, R=a hydrocarbon group, 0<x≤1 and 1≤y≤4.
 32. The powdermass of claim 30, wherein said lithium ion-conducting additive containsa lithium salt selected from lithium perchlorate (LiClO₄), lithiumhexafluorophosphate (LiPF₆), lithium borofluoride (LiBF₄), lithiumhexafluoroarsenide (LiAsF₆), lithium trifluoro-methanesulfonate(LiCF₃SO₃), bis-trifluoromethyl sulfonylimide lithium (LiN(CF₃SO₂)₂),lithium bis(oxalato)borate (LiBOB), lithium oxalyldifluoroborate(LiBF₂C₂O₄), lithium nitrate (LiNO₃), Li-fluoroalkyl-phosphate(LiPF₃(CF₂CF₃)₃), lithium bisperfluoro-ethylsulfonylimide (LiBETI),lithium bis(trifluoromethanesulfonyl)imide, lithiumbis(fluorosulfonyl)imide, lithium trifluoromethanesulfonimide (LiTFSI),an ionic liquid-based lithium salt, or a combination thereof.
 33. Thepowder mass of claim 28, wherein said electron-conducting polymer isselected from polyaniline, polypyrrole, polythiophene, polyfuran, abi-cyclic polymer, a sulfonated derivative thereof, or a combinationthereof.
 34. A lithium battery containing an optional cathode currentcollector, the cathode electrode as defined in claim 1, an anode activematerial layer, an optional anode current collector, an electrolyte inionic contact with said anode active material layer and said cathodeactive material layer, and an optional porous separator disposed betweensaid anode active material layer and said cathode active material layer.35. The lithium battery of claim 34, which is a lithium-ion battery,lithium metal battery, lithium-sulfur battery, lithium-selenium battery,or lithium-air battery.